A new OS probably won't be a cure-all if the hardware has problems. A 'clean' install would be preferable.
If you have access to a WinXP CD and run it, you will get a screen with 4 choices:
1. Install Windows XP
2. Install optional Windows components
3. Perform Additional tasks
4. Check system compatibility
Use #4 and you will have few surprises. If you are connected to the Internet at the time, it will update its database.
You can also download a 50MB advisor from Microsoft:
<a target="_blank" href=http://www.microsoft.com/windowsxp/pro/howtobuy/upgrading/advisor.asp>http://www.microsoft.com/windowsxp/pro/howtobuy/upgrading/advisor.asp</a>.