"Right click on the desktop (on any empty space, with nothing selected) and click properties. Next go to the Settings tab and you want to change ""Screen resolution"".
If your monitor has sent the correct information, you just want to move the slider up to maximum. If however Windows is reporting loads of settings (like in my screenshot), you want to just put it to the maximum that your monitor supports."
"Right Click on desktop -> Properties -> The rightmost tab
You'll have to forgive me if the details are wrong, it's been a few years since I last used an XP machine, but you probably want the resolution slider all the way to the right."
