My system has been stable for 1 1/2 years. I've learned a lot about keeping my system stable by visiting and helping on sites such as annoyances.org. I was under the impression that you could access your system fully by logging unto a different account. Over all these years of using Windows 95, 98Se and now XP, and Windows 2000 at work, I've learned a lot. I've also run and troubleshoot computer mainframes. I've found through experience that the best protection is Norton, period(Antivirus, Firewall, and the Windoctor). Spybot is also the best protection scheme for Spyware. There are lots of hackers with malicious intent in this world.
Windows messenger is also a dangerous avenue for malicious attempts to compromise the integrity of your computer system. I've learned to completely block it.
I've also learned to stay away from windows customizing programs that hack the operating system. I've also learned to stay away from programs that create possible conflicts with the operating system. Therefore, I'll never use StyleXP, Alt-desk, or any of those other windows customizing programs.
It's Object Desktop for me, or nothing.
I've also learned to stay away from, Microsoft Updates as a avenue for third party software. If you need updates for a Nvidia video card, or Soundblaster, visit their sites.
With that said, it sounds to me that you need a complete system restore. If you have a dell, I have heard many horror stories. I had the same problem with my Gateway system. I got rid of the Gateway Restore Disk completely. These manufacturers tend to leave out important parts of the operating system and it limits your systems flexibility. If you want XP, get XP. Get it uncontaminated by Commerical advertisements and promotions by one of these computer manufacturers.
Most important, troubleshoot. If you have a problem carefully trace it. Restore your system without conflicts, and then add software and accessories, one by one.
Once, I completely restored my system three times, trying to trace a problem. I found the problem was third party windows updates. Never install third party driver updates from windows updates. Visit your hardware manufacturer for updates.
If you want a stable system, learn to use your registry. And learn to defrag your system completely before installing new components or software.
MOST important during this learning process, is to back up your important files. This means by an safe external source such as a CDR. I backed up my important files to 2 different devices(external drive and CDR).
A complete reinstall for me takes two months. I won't take any shortcuts. shortcuts cause problems. Viruses can hide in your boot record. So, when I reinstall, I reformat my entire hard drive.
It's a learning curve. Good luck.