It probably won't be the graphics card - more likely the screen or its inverter that has gone. As Si suggested - borrow a VGA monitor and if you can use it without problems, your card is fine.
http://upload.wikimedia.org/wikipedi.../SVGA_port.jpg
Next step is the inverter. It's a little 1cm x 10cm board at the bottom of the screen (after you take off the cover). It should be about a tenner to replace.
http://clevoweb.co.uk/images/inv.jpg
Bear in mind that your whole screen might be dead. Mine has just gone belly up, and I can't really justify a £100 replacement, but I could justify the tenner that it took to confirm the inverter isn't broken.