I have just had Windows 7 re-installed. Before that I used the 32bit version of the OS which visually played Oblivion and other older games just fine. I forgot to tell the computer chap which version to install, and he forgot to ask me and went ahead and installed the 64bit version. Now I have a small picture of Oblivion with black sides.

The monitor is a Samsung SyncMaster with a native resolution of 1680 x 1050. I normally used to play OB in 1024 x 768 which worked out fine. Now it seems whichever resolution I try is the wrong one. Even the computer's desktop looks out of shape with each resolution I'm trying out. There must be an optimum one surely. Apart from the playing games aspect these resolutions are a real strain on my poor old eyes.

Can anyone with this monitor, or similar help me out please? Thanks.

Right click on the desktop and click "Personalize". Then go to resolution settings. Make sure that you have 1680x1050 set as the main resolution.