Probably not your problem, but some BIOSs have an option to turn off the PS2 mouse. Check that and see. Also, sometimes when a mouse has not been detected initially you have to force it to find it. Do this by using hand controls in the control panel and go to the "Detect new hardware" control. A little tricky to do by hand but you should be able to do it. Other than that, I would suspect a bad mouse, which you should already have troubleshot, or bad mouse port. Could always get a USB mouse.