Sounds like windows 9x. Upgrade to the NT series already and your troubles will go away.Also, you should've just reconfigured the mouse speeds (like doubleclick tolerance) and all would've been fine again. If something happens with the filesystem or registry in w9x, you can have pretty much any kind of things happen.
There are ways to get cheap legit versions of software. Windows 2003 just happens to be a server version, even the OEM version is more expensive than XP Also, where exactly do you have to pay $470 for XP pro? Checking the prices, that's about $100 more expensive than the local store. Also, if you upgrade from windows 98, you can get update version for even cheaper. And OEM prices are even cheaper than that. Since OEM versions are sold to anyone who buys internal component, some stores here sell OEM software to people who buy IDE cables
http://www.google.com/froogle?q=windows+xp+professionalI congratulate you for managing to find a ridiculously expensive store.