This time I finally got a new GPU Nvidia Geforce GTX 460 from a friend and I few minutes ago installed it and booted the PC but the monitor doesn't show any picture at all. Had an ATI Radeon HD 3600 before. Thanks!
Intel Core 2 Duo 2.67 GHz
RAM 4 GB
Windows Vista Home Premium 32-bit
//Solved it, seems there were 2 6-pin PSU connectors needed to be put in!
Edited by rei158, 24 July 2012 - 02:58 PM.