Did you install the motherboard chipset drivers? If not, that could be the reason. As Dell supports Vista (32/64 bit) it should work OK on Win 7 as the same drivers can be used.
Generally, on an install the correct install sequence is (1) Install Windows (2) Desktop or Laptop System Software (3) Install motherboard chipset drivers (4) Install Device Drivers including Video, Dell Sound, NIC drivers, etc.
Dell M1710 driver downloads Drivers and Downloads | Dell [United States]