I have a problem with a mouse that does not work on computer A, running win XP, when plugged into the PS2 port. The same mouse works on older computer B, running win98. The same mouse also works on computer A, when plugged into a USB port (it's a USB/PS2 mouse). Computer A, when booted with the mouse unplugged, does not prompt me to insert a mouse booting XP. Computer B, when booted, with the mouse unplugged, does prompt me to insert a mouse booting Win98. My best guess is that the motherboard (fairly new) is bad. Are there any other tests I can do to confirm this diagnosis?