There's always the chance of a screw-up, just owning a pc will get you there at some point. I would try Mack's suggestions first. MS system restore is very stable, I've used it multiple times on all 4 pcs in my home, never had a problem...at worst, nothing changed, but it worked to my benefit most of the time. (Haven't had to use yet on the wife's new "work" laptop... ). Having said this, you should always back-up your data. I'm pretty anal about this...keep a recently cloned hdd, so if I screw-up, I just boot the clone as primary and clone again.

In order for system restore to work, it must be enabled ( it should be enabled as a default setting) and have created restore points....couple ways to check. You can navigate via control panel or just click the start button > all programs > accessories > system tools > system restore. You'll get this window and hopefully be all set.