At some point in your computing life, you'll end up replacing an old machine in favour of a shiny new computer. But what should you do with your old PC?

If it's still working well, then throwing it out won't be the best move. It's bad for the environment and it might contain sensitive information. There are various ways to delete that data permanently, before you bin it or take it to a reputable electronics recycler.

But it's amazing how many people ditch perfectly good machines when you can do plenty of things with an old PC. In fact, here are a dozen ways you might put that old system to work.

1. Convert it to a NAS or Home Server

If you don't already have a NAS, this is a great use for a now-obsolete PC. Sure, you could pay for cloud storage for your family, but a NAS gives you full control over the security of your files, and means you can keep your music, photo and video libraries in one place for everyone to access.

However, it's not just a matter of connecting that old PC to a router and starting it up. Windows - especially older versions - aren't configured to be effective servers or storage systems. Plus, a PC might use too much power compared to a dedicated NAS box. You'll want to set BIOS power management to run cooling fans in quiet mode, if that option exists. You'll also need to set up the operating system so that it doesn't shut down at inconvenient times, yet run in a low-power state when it's not being actively used.

Bear in mind that you'll probably want to run your server 'headless' (that is, without a monitor), and sans keyboard and mouse as well. While you'll need a display and input devices for the initial setup, make sure the system will work properly without them. Having a scheduled reboot hang because the system halted during startup (it couldn't find a keyboard, perhaps) is annoying, to say the least.

Also, the operating system is likely not well suited for storage applications, particularly for multiple users. While Windows can function well as a storage repository for a couple of users, you'll want to take the time to create user accounts for each person who might need access. In some cases, you may want to set storage quotas.

A better solution would be to install a proper network operating system. One choice is Windows Home Server. However, that will cost you somewhat north of £70, and WHS may prefer newer hardware. An alternative is FreeNAS.

FreeNAS is open-source software designed to turn a PC into a network-attached storage device. It's based on FreeBSD, a UNIX variant. If you're uncertain whether you want to commit to an unfamiliar OS, FreeNAS can be downloaded as a LiveCD version.

This is an ISO file which, when burned to a CD, will boot off an optical drive and run completely from memory. You can keep your old OS on the hard drive until you determine if FreeNAS is suited to your needs.

2. Donate it to a local school

If your PC isn't too archaic, consider donating it to a local school or hospital. Even if it is way beyond its sell-by date it could go to a local school's computer lab (most schools have one) and be used as a test bed, to take apart and reassemble. Alternatively, local schools might use it for parts, although they may shy away from used gear, given the unknown pedigree or wear of older hardware.

As with selling a system, the final option in this list, you'll want to remove all software that you've reinstalled on your new PC. And make sure to include all licence information for the software you're leaving installed on the old system.

Bottom line: no charitable of publicly funded organisation is ever going to be unhappy that you are offering them a computer. Even if they can't use it, they may be able to sell it or use it for parts, and you can enjoy the healthy glow of a righteous person.

Some local authorities will provide you with details of local non-profit groups who may accept your PC. And Computer Aid International can send computers to underdeveloped countries, so long as the specifications are high enough.

3. Turn it into an experimental box

You've heard about this Linux thing, and maybe you'd like to give it a whirl. But the thought of trying to create a dual-boot system on your primary PC leaves you a little green around the gills. Now you can experiment to your heart's content on your old box.

Check out Ubuntu, the sexy Linux distro that geeks love to, well, love. The neat thing about Linux is all the built-in support for older hardware, so installation is usually easy. In fact, installing Ubuntu is sometimes simpler than installing Windows. And there's a wealth of free software for Linux just waiting to be tried out.

If you think you've got the tech savvy and a bent for tinkering, you might try creating a Hackintosh - a PC that can run MacOS. It can be done, but it does take a fair amount of effort. The main hackintosh site is a good place to start, but expect a long and somewhat bumpy trip. Oh, and you'll have to fork out for a legal copy of MacOS.

In addition, a number of true UNIX-based operating systems are available, ranging from FreeBSD or PC-BSD (based on the Berkeley UNIX version) to OpenSolaris, based on the Sun Microsystems version of UNIX.

4. Give it to a relative

I do this all the time. My brother-in-law has modest computing needs. So I'll often just hand over one of my two-year old PCs, though I'll usually drop in a mid-range or entry-level graphics card.

I don't generally recommend doing this with your kids, though - at least, not if your kids are like mine. They often need as much or more PC horsepower than I use on a regular basis (outside of gaming and photography, anyway). My oldest daughter is a dedicated photographer and makes heavy use of Photoshop, while my youngest daughter has become a pretty hardcore gamer.

Giving a system to family members can be fraught with peril, though. That's because you are now the go-to person for tech support. So you've been warned: Give a PC to a friend or relative, and you're now on call.

One thing you'll definitely want to do is completely erase the hard drive and reinstall the OS from scratch. If it's an off-the-shelf system from a major manufacturer, restoring it to its original state from the restore partition or restore disc accomplishes the same thing.

5. Dedicate it to 'Distributed Computing'

Want to do a little good for humanity? How about dedicating your old PC to one of the various public distributed computing projects?

The best known is probably [email protected]. [email protected] uses computing resources from all over the world to help study protein folding, an essential element to understanding how many diseases operate. If your old PC has a fairly new graphics card, that hardware can often pitch in as well, and offer up even more computing resources. Other distributed computing ventures include:

6. Use it as a dedicated game server

Do you have a favourite multiplayer game? If so, check and see whether it's a game where you can host a server on a local computer - you might consider making your old system a dedicated game server. Most multiplayer games capable of playing online often support dedicated servers.

The great thing about many of these dedicated game servers is how little system horsepower they actually need. 

7. Use it for old-school gaming

Related to the idea of using an older system as a dedicated game server, consider repurposing that box for retro gaming. You can go as nuts as you want. For example, install Windows 98, so you can run those older Windows 95 and DOS games, if you have some around. Lemmings, DOOM and Wolfenstein 3D are all classics now.

Note that oline services such as Steam are offering older games that have been rewritten to work under newer operating systems, and DOSBox lets you emulate a legacy DOS environment to get your classic gaming fix. So you can probably stick with Windows 7 or 8, if that's what the old PC is running.

Perhaps the most complete site for older PC games is Good Old Games. GoG, as it's often called, offers a large number of older titles, all of which work fine under newer operating systems. So if you've always wanted to go back and play Planescape: Torment, now is your chance.

If you want to go really old school, install MAME (multiple arcade machine emulator) software. That will allow you to play arcade games and games written for older game consoles, provided you have access to the ROMs and other related files to run the games. MAME can become a gigantic time sink (albeit a very fun one), so you've been warned!

8. Make it a Secondary Computing Server

If you're a content creator, having another PC to help with distributed rendering chores can greatly speed up final renders for complex projects.

Each application handles distributed rendering a little differently, so you'll need to consult your documentation. But typically, you'll install a lightweight application on the secondary rendering system, which will take data and commands from the primary system and then return results when done. The main application on your production system, or a separate manger app, manages the rendering across multiple networked systems.

9. Set it up as a light-duty 'Living Room' PC

We have a small PC in our living room that's often used for quick web surfing and to check email. Occasionally, our kids will come down and do homework on the communal PC when they get tired of being holed-up in their rooms. This can work particularly well if you have networked storage somewhere in the house, so people can get to their files whether they're on a personal system or a communal one.

If you do have this type of communal PC, your first inclination might be to create separate accounts for each person. I've found this isn't really necessary. Since it's communal, no one really keeps private information on it.

The flip side is that you'll want security software that's as bullet-proof as possible. Since you have multiple users on one system, eventually someone, sometime, will hit a website that may attempt to download a Trojan horse or other malware.

Here are the best antivirus packages to install.

10. Recycle it

Contrary to reports, it is that easy being green - but it's not always cheap. The simplest way to ditch your PC without damaging your conscience is to visit and find your nearest recycle bank. Your local authority should be able to collect the PC for a small fee, but some will simply dump it into landfill, so be sure and ask.

These days, legally, you shouldn't have to foot that cost. Under UK WEEE regulations, PC retailers are honour-bound to provide take-back facilities for customers to return old equipment whenever a replacement item is purchased - free of charge.

The standard and variety of service offers differs depending on the size of the organistaion. Some of the bigger ones, including Currys PC World, will recycle old electronics if you’re buying a similar product. Dell, for instance, will collect your old item for free, regardless of brand, when you’re buying a new PC. Others, like Amazon, will direct you to a designated collection facility for recycling your PC when you make a purchase. 

11. Salvage it

If you build your own PCs, you may reduce the cost of your new system by salvaging parts from the old one. Good candidates for salvage include the case (if it's not a proprietary system from HP, Dell, Acer and the likes), the optical drive, the power supply, and, sometimes, the memory modules.

Depending on how much you actually reuse, the distinction between new system and one that's simply been upgraded is a hazy one. If you replace the motherboard, CPU, memory, and primary hard drive, but keep the case, power supply, optical drive and graphics card, is that a new system, or one that's been upgraded?

That will still leave you with a few old parts. Which brings us to our last point...

12. Sell It

Somewhere on eBay, someone is looking for a computer. They may not be able to afford a new PC, or are looking for a second PC for the family. Your old PC, at the right price, may be just what they need. Assuming it all goes smoothly, everyone wins: you unload your old hardware, which finds a good home with a new user who can appreciate it.

Also, using an escrow site such as Paypal (required for eBay anyway) gives you a sense of security, as does both Seller- and Buyer protection on eBay.

As we've seen, an old computer can have many uses, particularly if it's still in good working condition. And not all uses for a PC require quad-core systems with high-end graphics. So if that old system is sitting in a closet somewhere, dig it out and put it to use. Who knows? It might be your PC that identifies the signal that's the first sign of intelligent life outside our planet.