Katie you should be doing back ups as a matter of course, not when you get a problem.

Rather then reinstall the whole of windows just go to restore and reset the computer to a point in time when your computer was working properly.

To remove and reinstall the driver

Disconnect the device from the USB port.

Open Device Manager.
Double-click the appropriate device category.
Right-click your USB device, and then click Uninstall.

If your mouse is not listed, this means that it was uninstalled automatically when you disconnected the mouse.
Restart your computer then plug the device into the USB port.

Your computer will detect the device and reinstall the drivers for it.

If you done the above and it still plays up a reinstall won't do much as it will load the same drivers. A good scan for any norty software and a defrag could help it certainly won't hurt.

Since this affects your PS2 port as well i don't think it will be your Universal Serial Bus Controllers (USB Controllers for short)

Before you go and change out the motherboard i'd buy a better mouse and see how i get on with that because if it still plays up you got a good new mouse to go with the new motherboard and other new bits as well so the money you spent won't be wasted.