I just recently build a new computer with a micro atx nvidia motherboard and a AMD athlon 3700+ 2.2 ghz processor. I put in my old hard drive and my old Nvidia 7300 GS and my existing Gig stick of ram and a 512 stick, then I booted it up. It started up fine and it looked like my old computer. Ehrn I went to go play a certain game that needs a lot to run it, I notice black flickers in my screen and words writing over top of each other, just things that don't look right. Is this because my graphics card got damaged or is it because my system isn't getting enough power, I am running a 350 watt power supply.
Did you installed all of the drivers needed???, once you replace motherboard and processor it's not as just put your old disk, there are some issues that changes and it is normally better to reinstall the O.S. and the drivers for the new motherboard, can you tell which motherboard and processor had in the old computer?? which Operative system are you running??