Make sure your antivirus software is up to date and run a virus scan.
Download, install and run Ad Aware:
www.lavasoftusa.com.
Check the error log for recurring errors. Open Control Panel, open
Administrative tools, open Event Viewer, look for recurring errors, double
click, the information contained within may give a clue as to what is
hanging your system.
Be sure your drivers are up to date, check the device manufacturer's
websites for the latest drivers.
Assuming you have an actual XP CD, place it into he drive, when the setup
screen appears, select "Check System Compatibility," it may find issues on
your system that need to be resolved and might be the source of the issue.
If you don't have an actual XP CD as opposed to a recovery disk, the wizard
can be downloaded from the following site:
http://www.microsoft.com/windowsxp/pro/howtobuy/upgrading/advisor.asp
Since this is a recent issue, you might try using System Restore to take you
back to a time prior to when this started. Start\All
Programs\Accessories\System Tools\System Restore. I listed this option last
because it might be useful to find the source of the issue because if you
simply restore the setup, you might repeat whatever action was responsible
for this to begin with.