That's my problem. My monitor does not support 640x480 resolution

I have a Viewsonic VX1940w, so I looked it up and found this comment in the feedback...
Cons: Does not support 640x480 @ 60hz. It displays the video but cuts off the top and bottom of the screen and there is no options for vertical size. Tech support said "it does change your settings on your video card". I use this monitor for computer repair so I can't change video resolutions when in BIOS or windows installer. I think its a glitch by viewsonic since it works fin at 75hz.
Makes more sense now that I know this.
It won't let me change from 60hz to 75hz either. I'm making this game for other people to play anyways. So I'm assuming that full screen should work on most other monitors? It's just mine that's being a pain.