I recently bought the 1GB GDDR5 Radeon HD 5830, installed it, and it worked like a charm. I played WoW and kotor on max settings the last few days. It was working perfectly and I was really happy with it. Today, while I'm playing WoW, my computer locks up all of a sudden and I have to reboot. When I do I get no display from my graphics card. However, I do get display from my onboard graphics.
I decided to let my computer chill for a while and came back a couple hours later. The same thing happens. The onboard graphics works, but the card doesn't. I then try taking my graphics card out and reconnecting, but it was no use.
When my computer runs, the graphics card runs too so I'm not sure what's happening. I need some help.
AMD Athlon II dual core 2.9 GHz
6GB Patriot DDR2
ASUS M2N68-AM PLUS
1GB GDDR5 Radeon HD 5830
Sentey 450 Watt PSU
My best guest ? Your graphics card just died. It happens sometimes. Just return it and ask for a new one ! It's not fun when it happens to you, but know that you're not alone in this !
An other, and a lot more improbable, explanation could be that your PSU kind of half-died. Since your dedicated graphics card draws a lot more power than the on-board one, it could be that your PSU wasn't able to cope with the new demand and failed, but not completely. If you have multiple rails on your PSU, it could be that one failed.
Anyway, the simplest way to find out is to replace your graphics card with a new one. If it still does not work, then it's your PSU that is defective.