If you install the video card driver correctly, the video card should "talk" to the monitor through the cable and tell Windows what resolutions the monitor supports.
Download the latest driver for the video card (amd.com , support button on right) and install it, then reboot.
If you're using VGA cables (and you shouldn't), in some cases the video card can't get information from the monitor through it, so you have to tell Windows and the video card what resolutions your monitor supports.
The easy way to do it is to add dd the driver for your monitor - if you don't have it on a CD, go to the website of the company that made the monitor, go either to the support section or in their products pages and look up your monitor and there should be some drivers there.
If they don't give any driver, you can still use a software like "Powerstrip" to create custom resolutions and refresh rates.
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I'm not too bothered about PC related questions but imho they should not be posted in " Electronics » Projects, Designs, and Technical Stuff » " - you're not designing anything. Put it in General chat or "beginners" maybe.