Computer hardware problem, please help!?

[stanlei 100]

ok, i sort of asked this question earlier but had no luck so im going to re-phrase it -P I dont really know alot about computers but i am an electrical engineer so have a good understanding of the basics! Anyway.. I went to turn on my pc and nothing happened, it was completely dead. I swapped out the PSU for another one (the one in my sisters computer LOL) and it seemed to fire up fine. However, this PSU is only rated at half the wattage of the original so i only connected the motherboard and the video card to be on the safe side. The problem i have now is that the monitor says it is not receiving anything(The internal fan on the video card fires up so i assume it is working). Is this because my HDD does not have a power supply to it and that is where the drivers are located for the video card? Any help or suggestions would be appreciated thanks If it matters its an asus an8 sli premium motherboard and a geoforce7800 video card

[Eppy 3,446]

um the HDD always needs power you can boot past the BIOS without a HDD...what wattage PSU did you go from

[Sledgstone 8,672]

Your computer does load the bios screen right? Without the harddrive powered up, you should still at least see a screen with the bios settings. If you're not getting that then your psu or motherboard are having an issue. It could be your psu is too underpowered for the cpu. Then again, if your old psu took a powersurge, or just fried itself, it could have damaged your motherboard at the same time.

[gokuDX7 2,871]

Just buy yourself a good 750watt-1000Watt PSU and call it a day.