|It doesn't recognize it when in the OS or just in the POST screens?|
If the OS then the most likely reason is that you haven't installed the motherboard chip set drivers. Win2000 is older than your hardware so the correct drivers are not included in the CD. Get them from the manufacturer of the motherboard.
If you don't know the model of the board then download SIW and use it to determine the model. Get SIW at the link below.
Additionally, your custom featured mouse needs it own drivers installed.