most phones/pcs have problems like this,
try going into
system/addremove programs
remove the files associated with the phone
remove the usb cable from the pc
reset the pc,
plug the phone onto the cable,
wait for windows to fully load,
plug the usb into a different plug than it was before (shouldnt but does seem to make a difference)
wait for windows to find it,
it should be found as a mass storage device, smart mobile phone, external drive, flash card, flash memory device, etc
you should be able to see it within "my computer" as an individual disk drive?