Well, there are two things that are very common with axons not being detected by the pc when they previously were.
1. The axons usb plug has a cold joint, this means that the pins on the usb connector aren't being connected to the board. This can be detected by using a multimeter and placing one lead on the usb pin in the connector and the other lead in the corresponding trace. If there is no connection this is most likely your problem.
2. The cp2102 is fried, this isn't to common but it has happened, check if your 3V3 output pin is working when the board is powered.
Alternatively their have been some axon issues with vista posted on the forum a while ago, search and you may find the problem.