If you have not set up X-Server on your Desktop or forgot about it, here's your guide to do so.
First, as root, type Xconfigurator at your console. The X-configurator Program will now run and should detect your video card. Choose your monitor settings according to your monitor manual. If your card is not detected you might have to enter the details properly yourself. To see if your card manufacturer has released a driver for your card, please do visit their site. Now Linux supports a whole bunch of cards and you should not have any problem with the detection.
The next step after setting up X-server, would be to type startx to have your GUI up and running. Enjoy it! Choose GNOME or KDE depending upon what you like the most.