Common issues causing Windows XP to run slower:
1) Only 512MB ram. All the security updates and other updates for XP to get you to SP3, take up more memory. Add memory and get an instant speed boost.
2) Running McAfee, Norton, or AVG. I have found that these 3 anti-virus software really slow down your computer. Try Microsoft Security Essentials. It’s free and uses little resources. Most problems today are caused by spyware, not viruses.
3) Spyware and Malware. If your searches on the internet re-direct you to another site or you are getting pop-up windows, you have spyware. Use the links on the right to get ride of the spyware.
Hope these tips help.