You need the correct driver for windows and the card for your dell. Go to support.dell.com, click home use, click drivers and downloads, on the screen that pops up enter your service tag digits (on a white tag located somewhere on the pc). On the next screen, select windows 7 for the OS (if available) and go down to video cards and find the correct driver. Download it, install it.
If the driver is not available, you need to find out if you PCI-E, AGP or just PCI slots available in your pc, then hit up a retailer or website and order the APPROPRIATE card for the type of slots you have available.
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