[astroglide]

there is virtually no chance that defragmenting will help. it's possible that you're having cpu/io spikes while playing if you're using pokertracker and some sort of heads up display while you play and your computer isn't particularly fast. you can check your cpu/memory utilization by hitting ctrl-shift-esc and looking at the performance tab while you play.

it could also be usb lag. even if the bus isn't saturated some devices will spaz out when specific other things are active. you could try plugging the mouse into a ps/2 (small round circular) port. you'll need to either use or remove the adapter that came with the mouse when you bought it. if doing that corrects the problem, it's likely a usb issue and you should start looking at anything else that's plugged into a usb port.