Hello, I recently purchased some upgrades for my system, these are the specs: AMD Phenom II X2 Dual core 550 3.10GHz Silver Power 400W SP-SS400 PSU Gigabyte GA-MA770-UD3 AMD 770 (Socket AM3AM2+) PCI-E Motherboard XFX ATI Radeon 4850 GFX Card. Also have a CD-drive & 2 x 120mm fans connected. My problem is that the system will not start at all. Nothing at all happens when I press the on button. As far as I know everything is connected properly. I've read and re-read the instruction manuals, checked all the connections thrice-over and also used the guide on these forums to build this PC. I'm beginning to question whether my current PSU (Silver Power 400W SP-SS400 PSU) is powerful enough to run this system. but even then, surely I should get some sort of flicker of power or a dodgy-boot? So basically, I am asking for some help to solve this problem. Thanks alot, desmond.