No you don't have to uninstall the old mouse drivers, just plug the USB mouse in and PNP (plug-n-play) will ask for the new drivers. Read your instructions, usually on most USB devices you plug up the USB device while the PC is running and PNP takes over from there. The mouse drivers will install on top of the old drivers. You shouldn't have any problems as long as you install the correct version drivers.
<font color=purple><b>Listen twice as much as you Speak, better yet Think twice. :wink: </font color=purple></b>