Right click on the desktop.
Choose properties in the menu.
Choose the Settings tab.
Click on the Advanced button.
Choose the adapter tab.
Make sure the adapter is what you expected. If you're not sure look in the documentation that came with your computer.
Now choose the monitor tab.
I suspect that somehow your monitor driver got changed. (Yes there is a monitor driver - at least that's what ms calls it.)
Click on the properties button.
You'll have to poke around in this area. I've never had to fix up a situation like this. Roll back driver, and uninstall look potentially useful.
You might also try calling the
SVA people to see if they've got a monitor driver file for your monitor.
All of the above assume XP, but later versions should be similar.
Actually, did you check in your stuff to see if you got a cd with the monitor? I did when I got my samsung.
Good luck.