how to change screen resolution from or before my app progrmatically.
I have designed all my screen for 800x600 and any other resolution dont show them properly.

If I installed an application on my machine and it changed my screen resolution, the first thing I would do would be to uninstall it.

You should re-size your forms depending on the screen resolution instad of the other way around.

Check out SYSMETRIC() in the on-line help. If you are using VFP 8, BINDEVENT() makes resizing even easier.