If you post up the brand and model should be able to tell you, generally the highest resolution offered is the native one which if you have a recentish widescreen lcd monitor will likely be either 1680x1050, 1920x1080 or 1920x1200.
I have Samsung Syncmaster B1630 with a native resolution of 1360 x 768. Its ok if I if I plugged in VGA but when I plugged in DVI with an adapter the resolution seems different. Whts wrong? Should I discard my DVI adapter or just stick to VGA. Thanks for the reply!