You've finally gone and bought a new PC. It has a boatload of memory, lots of cores, and a fast, modern graphics card. But now your old computer sits in a corner, and although you know it's just a machine, it seems to be sulking like a puppy that missed its morning biscuit. It's weird, but you feel guilty with the whole idea of throwing it out.

After all, it's perfectly functional. When you first bought it, it was near state-of-the-art. If your new PC replaces one that's really on its last legs, by all means, take it to a reputable electronics recycler. But it's amazing how many users ditch perfectly good machines when they pick up a shiny new system.

You can do plenty of things with an old PC besides sending it to the recycling heap. Let's take a look at a few ways you might put that old system to work.

1. Convert It Into a NAS or Home Server

If you're running a home network and have multiple users--you, your spouse, your kids--reuse as network-attached storage or even as an actual server may be just the ticket for an old system.

However, it's not just a matter of plugging an old PC into a network connection and starting it up. Most desktop systems aren't configured to be effective servers or storage systems. For one thing, they probably use too much power. 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 XP, Vista, or Windows 7 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 $100, 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 daycare center. Worst case, it could go to the high school computer lab (most schools have one) and be used as a test bed, to take apart and reassemble. Alternatively, the school district computer services group might use it for parts, though it's been my experience that many school district IT groups tend to shy away from used gear, given the unknown pedigree or wear of older hardware.

If you donate it to a daycare or child development center, consider buying some low-cost educational software packages and preinstalling them before handing the system over. Also, as with selling a system, you'll want to remove all software that you've reinstalled on your new PC. And make sure to include all license information for the software you're preinstalling on the old system.

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.

In Video: How to Install Ubuntu on Any PC

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 X. 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 pony up a few bucks for a legal copy of MacOS X.

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.