Lost screen resolution after upgrade to Win7

Before upgrade I had a max screen size of 1280 x 800, and if I set to a smaller size, the image still filled the screen. This size is of course WXGA .
Since upgrade I have a max of 1028 x 768 which does not fill the screen, and if I choose a smaller one,e.g. 800 x 600, the image visibly shrinks still further.
I am told that I may need a new driver ; now the machine specification, and the label on the machine say the graphics is Nviidia GeForce Go 7400 GPU , but when I look at Device Manager it says that the Display adaptor is " Standard VGA Graphics Adaptor"
Have I somehow ( in the upgrade) lost the Nvidia set and gone to something else on the motherboard ?
And how can I get my full screen back ?

I tried that - when I tried to run the file I got the massage that it was designed only for Operating Systems XP , Windows 200 etc - and would not run on my Windows system.

see this link:
VGN-SZ5MN_B | VAIO and Computing | VAIO | Downloads : Sony, Technical support