FYI. I found this on another forum. It seems XP may have your L2 cache set lower than it should be. My factory specs say the L2 should be 512kb and XP had it set at 256. I changed it to 512 and it appears to have made a slight improvement.
1. Launch the Registry Editor (Regedit.exe).
2. Go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Contro l\Session Manager\Memory Management.
3. Double-click SecondLevelDataCache DWORD value.
4. Using the options below, change the value in the Value Data text box to a number that matches the size of your Level 2 cache. Then click OK. Level 2 cache Value Data setting
Yep. Seems like Windows goes out of it's way to make things hard on the enduser. I have a nephew that works on computers for a living and stuff like this has made him a Linux fan.
If your computer is a off-the-shelf model, you should be able to get the specs from manufacturer's support page for your model, look for product info. Otherwise, check the processor manfacturer's website. I know Intel list the cache size on their site.