HD4850 doesnt work well...

[ALPRAS]

Hey there!

I recently switched my Nvidia Geforce 8600 GTS for an Ati Radeon HD4850, and I dont know why, the pixels went strange, always flashing and particles of the place... This happened to me some games such as Just Cause 2, Doom 3 BFG and Dead Space. But Team Fortress 2 works fine...
I've formatted the disk, re-installed the Windows, installed the correct drivers, but the problem presists... What can I do?

Here's my specs:
Intel Core 2 Duo E2200 2.2Ghz
Gigabyte HD4850 512MB
DIMM 4GB RAM
500GB SATA

 

[noidea_77]

Is it a used card? Could be a hardware (memory) problem.

 

[ALPRAS]

Yes it is. But the seller said that the graphic card was fine, and that the only problem was that it was making some noise, but that could be de dust...

 

[ALPRAS]

If it is a physical problem, can it be fixed? And it's going to be expensive?
Since I bought it in second hand, i'm afraid i can't return it :/

 

[ALPRAS]

I discovered that my PSU doesn't have sufficient power to the graph. I was looking for info about this, and I found that the graph needs a PSU that can give 36 amperes, and my PSU only gives 28. Could this be the real problem? The previous owner of the graph had a 550W PSU and said that before he sold me the graph she was great...
Should I give it a try and buy a new PSU? And how powerful should it be? I found one for 17€ (+-20$) with a power of 500w... It is enough?