>Is it possible like i can do with 680x480 in file's Properties -> Compatibility tab.
>When i close the application it then switch back to default resolution.
>How could this achieved in Windows XP?

Changing the resolution of someone's computer is a very bad idea. People set their resolution the way they want it, and arrange their desktop accordingly. If you change their resolution, you're going to mess up the desktop, and you're showing disrespect for the user.

What you could do is issue a message that says "This application works best when your display is set for 800x600." However, the best solution is to write an application that doesn't care what the resolution is.

Tamar