Here are a couple of tips I've found for having Windows XP run better:
1) Monitor user handles. The more handles in use on your system, the SLOWER your system gets. It shouldn't exceed 9000 handles really and if it's over 12,000 your system will start to crawl. How to monitor:
Ctrl-Shift-Esc. Then click on the Processes tab. Then click the view menu item and choose select columns. Select handle count. Start sorting by handles in use. Anything that uses over 1000 handles is probably evil.
2) GDI objects. Similar to handles. Beware of them. Same process as handles except choose GDI objects. ICQ is a huge pig in this area. People may put down visual styles or WindowBlinds or whatever but compared to ICQ, skins are nothing.
Handles and GDI objects are amongst the lesser known system killers out there.
Hope this helps.
