Also, don't use the charger cable that came with the phone, it only works well with WinXP. Use another [higher quality] 2.0 USB cable. Win 7 is sticky about that.
My charger cable is the only one (of three) that works on my Win 7 machine. I have downloaded the USB drivers from Sammy's site & reloaded them a few times. I keep the zip file where I can find it easily. Usually it works fine but ... seems like there's something not quite right in there (USB drivers, that is).
Mine used to work too, but now it don't. I am betting it was some kind of Windows Update that screwed it up for us. If we could figure out which one, we could uninstall it and it would probably go back to working again.
Plug your phone into the computer if it only shows charging turn your phone off then back on. Remember to leave the phone pluged in the entire time. This has worked fo me every time on win7 and vista