How do I change Windows XP screen resolution?

I know how to change it. But, when I try to drag the arrow-thingy across, it won't let me. It doesn't move....How do I change Windows XP screen resolution?
Try Installing Display drivers (which comes with motherboard CD) If ur monitor supports higher resolution it should definitely move...i hope i have helped u...How do I change Windows XP screen resolution?
First are you attempting to make it smaller or bigger. If you are attempting a resolution your system does not support it will not allow you to set it. Also does your system know what type of video card and monitor you have? On the same screen you can change your resolution, it should say this monitor on this video card.

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