how do i reset resloution size back to normal

someone got on my computer and messed with my resloution for gmod and mow all i can see a a small square in the top left cornner i cant even see the opptions can someone help me

Delete your garrysmod/garrysmod folder.

I believe there is something you can do in the launch options. http://lmgtfy.com/?q=setting+resolution+in+launch+options+steam this google search should do the trick. just click on the first link, if it works for counterstrike it should work for all other source games.

Oh, and resolution and graphical data is stored in the registry, so Sylerr’s idea wouldn’t work.
HKEY_CURRENT_USER/Software/Valve/Source/Garrysmod/Settings/ScreenWidth
HKEY_CURRENT_USER/Software/Valve/Source/Garrysmod/Settings/ScreenHeight

dont worry i found out if you just restart and that fixed it