See if DMA is enabled in WinXP. The only reason that I can think of that would cause the mouse cursor to skip when loading programs is your hds being in PIO mode. This uses 100% of ur cpu time to load programs from the hd into memory (which sucks). DMA bypasses the processor, and is one of the most wonderful things ever. Anyways, in XP if you don't know how to check if your drives are DMA, do this:
Right-Click MyComputer, goto Properties
Click the Hardware Tab, then the Device Manager Button
Select the IDE ATA/ATAPI Controllers and expand it.
Right Click on the Primary IDE channel and select properties.
Select the Advanced Settings Tab.
This will tell you what mode your hds are running in. If its in PIO mode, then thats your problem. If they are in DMA mode, then its something else that I cannot diagnose yet.