I recently changed my pc's motherboard. afterwards I did the set up only to realize that the mouse cannot be detected by the computer system. how can I solve this problem?

Is this solved yet?

Is it a PS/2 mouse or USB? If it's USB, does it pop up as an unknown device or anything like that? Do you have drivers for it that you should install first (these usually just add additional functionality though rather than being necessary for normal operation).

If it's PS/2, it may sound silly, but make sure that it has a secure connection to the PS/2 port, especially during boot. A lot of times if the keyboard or mouse connector isn't firmly seated during boot-up the PC won't know it's there and it will require a restart with a good connection before it will work (i.e. seating it after it's running wont' fix the problem).