Installed windows 7. Screen flickers

Yesterday I installed Windows 7. Then something strange happened. The screen began to flicker. This would happen when I load some types of software but not others. I couldn't really detect a pattern to it.

Let me describe the symptoms a little more. A lot of people use the word 'flicker' to mean that something strange happens to their image. In my case anything visually recognisable disappears completely and instead I see a bunch of purple lines moving. I've had this problem before with XP. However, in those cases it only happened when I was playing games. If I alt-tab out of the game it went back to normal. This is no longer the case. The only thing I can do to restore the image is to reboot the system.

I thought it might be a driver issue. I had the default windows driver installed. I downloaded the latest driver from NVIDIA. Installed it. Then the problem got worse. Every time windows starts up I get the same thing; the flickering or whatever you want to call it. I then boot up the system in safemode and uninstall the driver. I'm now using the computer without a display driver at all.

I thought it might be a bios problem (reading some forum posts that I thought might be related suggested that). I updated the bios driver, reinstalled the display driver, but the problem was the same. Not sure what to do.