Do you still have the old XP computer? If so, does it still connect? I ask because the cables are pretty fragile and one possibility for no computer link is a defective cable. You've already tried all available USB ports which was a very good test.
The other possibility to be ruled out is the nc status. Can you confirm that the nook color is turned on, not asleep, and that if a password was set, that you've entered the password?
The only time I had an issue like this was that my "new" refurb nook simple touch purchased on ebay (but sold directly by B&N, the ebay seller) arrived with a defective cable. When I was sent a replacement cable, it immediately connected with my Windows 7 PC.
