Resolution stuck on Mandrake 9.2 on Dell Dimension
 

I just bought a new Dell Dimension desktop and installed Mandrake 9.2.

When the resolution is at 640x480 things are kinda fine. The menu bar goes right across the screen and most things look good. Some programs though think they screen is way bigger and make themselves too big.

When I increase the resolution, the number of pixels diplayed seems to be the same but everything thinks the screen is way, way bigger and most of the windows etc. are only partly visible. When the mouse moves to the edge of the screen, it scrolls across untill it reaches the "real" edge. I get a higher resolution to display all in one screen.

Is this a hardware/vidoe/monitor problem or is KDE/Genome doing this screen scrolling? I don't like it.

Thanks muchly for any help.