First, because such things can be caused by malware, please download, install, update, then run a full system scan with free AVG Antispyware from the link below:
b]Ewido/AVG Antispyware 7.5 Tool
If malware is not the cause, then open the "Control Panel", double click on the "Mouse" icon, then click on the 'Pointer Options' tab, then UNCHECK the box next to "Enhance Pointer Precision".
If that doesn't help, try swapping in a known good keyboard and mouse.. See if it's simply a hardware problem.
Hope this helps.
I have searched for a similar thread and don't find one so am starting a new one. My problem has to do with insertion point as I type. For some reason I can't discern, as I am typing the cursor jumps to a random previous position and I am typing into an earlier line. I'm quite sure I am not striking anything but letter keys. Why is this happening? (HP Pavilion, Pentium M, Windows XP Pro, srvPk2)