Re: Window Lag and scroll lag?!
The first thing to do upon reinstalling Windows is to make sure the drivers/software for whatever is needed for the board are installed. That will effect memory controllers as well as any use of onboard sound since you are most likely running a separate video card.
If you are running an older ATI model card from the 9xxxx series the newer then 6.5 Catalysts won't work. This would on models like the 9250, 9500, 9550, 9600, 9800 all-in-wonder models. Drivers for those older cards are found at places like guru3d.com or omega at this late data. The latest 7.x catalysts are geared for Vista not XP.