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There's a good chance that you have an old PC lying around. Instead of letting it go to seed, turn it into a guinea pig for running new software, visiting unfamiliar Web sites, and performing other tasks that might otherwise leave your primary PC plagued with viruses, corrupt files, or other problems. You don't have to use a second monitor, and if you have a network, you don't even have to make extra room for the case on your desk. All you need are a keyboard-video-mouse switch, and two software programs.

A KVM switch lets you run a second PC from your primary PC's keyboard, monitor, and mouse. A hardware switch and cables--which tether yours second PC to your desk--cost about $50. Kavoom's $30 KVM program (free trial) is a software alternative that lets you remotely control a second PC located anywhere on your network.

Virus protection software and firewalls help prevent PC problems, but the best way to protect your guinea pig PC is to reinstall Windows and your applications, and then use an imaging program such as Acronis's $50 True Image 10 or Symantec's $70 Norton Ghost 10 to restore this pristine system image after every session. Refreshing my test system with the original image of Windows XP, Word, Excel, and all my day-to-day software applications takes less than 10 minutes and guarantees me a virus-free, perfectly running PC any time I need it.