I have an Asus radeon 4850. I always use the sleep mode in vista but this time the when I tried to wake up the pc suddenly shut down and didn't work afterward.

I thought at first that the problem was in the psu (Gigabyte 550 watt ge-p450p-c2) but after I test it with a coolmax tester it was working fine.

I unplugged everything and connected only the main power and the cpu connectors and the pc worked again. I tried to connect the pcie power to the 4850 card and when I tried to power it on it didn't run.

I tried an ide to pcie power cable and it didn't work also.

I plugged in a geforce 8600gt card and the pc worked again.

Also the card is underclocked because it was very hot and the pc always shuts down when the card is in use.

my setup:
cpu: intel q9300
m/b: gigabyte ga-ep31-ds3l
ram: 4gb 800
psu: Gigabyte 550 watt ge-p450p-c2
vga: Asus eah4850

I tried to unplug the pcie power and the pc could start but couldn't boot

I plugged the pcie power again but the pc couldn't start.

I tried another vga (6800gs) with pcie connector and the pc starts normally.

I have a noname brand psu and connected two ide power to a pcie power adapter and connect it to the pcie power of the 4850 the pc could start and the 4850 and the 4850 fan was blowing fast but the pc couldn't boot.

I installed the 4850 to another pc but with poor psu and the same thing happened again.

I don't know if the problem is in the psu or the pcie connector of the 4850.