That's usually on a home built machine so tell us if you tried installing the motherboard driver package.
I've an Orange SPV M3100 which has synched fine until this evening. Now its
not detected at all. I've shutdown and restarted my pc twice and the same
with the smart phoen. I've uninstalled Activesync (v4.5) and reinstalled it
but its still not detected - all the settings are the same as they were
yesterday - the cable seems ok as the phone is charging when connected to my
pc (Win XP Pro SP2)