ATI Radeon X1300 - Boot/Startup Problem

[Axel_F]

Hi
I recently got an ATI Radeon x1300 (256mb) video card. I installed it into my system properly. I boot up my computer, the card is powered, but all that comes up on the screen is colored bars, and then the screen goes black. It does this again and again, and doesn't boot up properly. What did I do wrong?

I have:
Windows XP SP2
512 MB RAM
Gigabyte Technology Co., Ltd. GA-7VM400AM(F) Motherboard
AMD Athlon XP Processor (2.1 GHz)

Thanks for any help.