There are many reasons for a particular computer to run
slowly - some are legitimate and some are not.
Do you have a good anti-virus program and do you use it?
(i.e., keep the auto-protect feature 'ON' and update and
run the main program weekly). You can get your computer
checked at the following site but should really have a
program on your computer for the auto-protect feature.
http://security.symantec.com
Are you behind a firewall (i.e., router) or have you
enabled the XP firewall? Do one.
Have you downloaded Service Pack 1 and other applicable
Microsoft updates?
http://v4.windowsupdate.microsoft.com/en/default.asp
Have you checked your computer for
spyware/parasites/trojans and etc.? Search via Google for
SpyBot and for AdAware (both free). Use both. Update and
use daily.
Other sites of interest:
http://www.michaelstevenstech.com/
BlackViper.com
http://www.aumha.org/a/parasite.htm
Bill