I have to replace my old graphic card (ATI radeon HD 2350 I know it sucks lol ) with a new one because of crashing down computer black screen, overheating and so on... I was looking something cheap like ATI radeon HD 5450 1024MB. I'm wondering if will it fit to my old motherboard http://81-208-25-53.ip.fastwebnet.it/Manuali/HP/Pavilio... and my PSU wich is 300W. And what about that PCIe 1.0 to 2.0 to 3.0 compatibility? thx in advance! Sorry for my bad English!