Nvidia 6150 onboard graphics problem with Win 7

My system:
Motherboard: Foxconn 6150K8MA
Graphics: Onboard Nvidia 6150
Ram: 3 GB DDR
O.S. Win7 Home Premium 64 Bit

Problem: With Win XP (before upgrade to Win 7) showed graphics ram to be 256MB. Now, with Win 7, shows only 64MB graphics ram ( I used CPU-z), and video playback and games are now much worse. I can't seem to find anything in the Bios that will enable me to assign more memory to the graphics. And yes, I have tried all the latest Nvidia drivers, to no avail. Am I missing something? Any help will be appreciated.
Many thanks.

Strange, my father has a rig with that chipset and it works fine (256 MB) with Win7 with default driver.

~edit~

Welcome russellbennett :)

Check this setting in the bios,