Im having a problem connecting my sync

I just got a sync from an individual, not a store so I dont have any software and I bought a rocketfish usb cable from best buy, and oddly it fit in the phone but didnt have a707 listed as a compatible model number but the guy working told me it would work for sure. I downloaded the usb driver off the samsung download page as well as PC studio three. But my phone still wont connect, it charges buy wont connect. If anyone could please help me out I would greatly appreciate it.

Thanks in advance guys.

Make sure bluetooth is off and check the phones connectivity settings and make sure it is set to PC Studio. Go to settings, connectivity, select USB mode, PC studio. If that is not the problem the cable must be the problem. The phone should connect in MTP mode even if media player is selected under USB mode. I think after market cables and chargers are a problem with this phone.