add/remove window scrollbar

Hi all

I'm having problems with my add/remove window. The scroll bar (the one that
goes up and down on the left) is not moving in time with the mouse. It is
like it is loose and when I move it past the middle position it speeds off
causing the mouse pointer to fly off the page. LOL.
It is only the add/remove window that is affected.
This is not a major problem but I would like to find out what is causing it.
I have just clean installed xp home with all the xp updates updates and I
have checked for virus's it is still not working correctly.

Any help or advice would be great. :-)

Thanks

Joe D