Or go to your "USB to PC settings" and take off "advanced networking" i know that works too. OR
Go to this page and install the qpst drivers that whitey10tc provides and try it then, its #4, and i use Vista and the active sync didnt install on my laptop but i guess i didnt need it cause my phone was found without it after i installed the drivers.
http://forum.ppcgeeks.com/showthread.php?t=94338