Plug and Play Monitor Screen Resolution Problem

Recently i found a monitor that i could plug into my laptop. I don't know what make it is however i do know it's 1280x800, the same size as my laptop.
I plugged it in and i noticed the resolution on the monitor isn't full screen so i pressed the menu button and scrolled to the reset option. Pressed it and no improvement. I fiddled around with the h position, v position and h size. It's improved however it's still not full screen. I the tried pressing the auto button on the monitor, then it made it worse :/
Anyone know how to fix this?

you have to set the resolution in windows, then if necessary use the auto adjust feature (maybe more than once). you should virtually never need to adjust the h pos or v pos.

Forgot to say im on windows xp.To set the resolution, i would have to go into display properties?EDIT: Thanks loony got it working :D