I have a really nice Dell latitude D820 laptop for work, but one thing that's annoyed me from day one is what happens to any open windows when I close the lid....they resize to like 640x480.

Probably not a big deal for most people, but with work sometimes I have like 20+ windows open, which means if you close the lid they all get resized and stacked on top of each other like the good old windows 3.1 days.

Anyways I finally found out what was causing it, it was a registry settings for my Nvidia video card.

Go into the registry (regedit.exe). [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Video] and find all the keys named “LidBehavior“ anywhere under this folder. (HINT: once I got to [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Video], I had to drill down 2 or 3 levels in a couple different places. I found 2 LidBehavior keys.) For each LidBehavior, change the value from 11 to 10. Reboot. Problem solved.

The above quote came from this website.