I have been trying to sort my computer but cant seem to find the root problem. When I turn power on at mains computer start up before I push power on button. Only the fan COMES on. When holding on on off button nothing HAPPENS just the Hard drive light seems to show as on but not flashing.

I have trouble shooted the fault by opening the computer up and taken every thing off so it was just motherboard and fan and does the same does not seem to detect that the ram and hard drive is missing? I changed the power supply and doing the same? The only thing I have done is added ddr2 ram from another computer but noticed the ram pn the computer is ddr?

I have just tried to hold the power button on and it seems like it TRIES to start is not able to start up and the fan spins faster?

Any ideas what else could try?If possible, I would try a new power supply (PSU)Ok I have added an old power pack that was working on this computer but now has the same problem. I did take a power pack off my sisters computer which was working ok since then I added new power pack and added wrong ram which did not notice was wrong type until I switch on computer. If I hold the power on button down the computer seems to try start up which would make me think it was something to do with the power pack? Could the wrong type of ram had any effect? Or could it be the power pack is not as powerful as needed? Its more less the same one as the computer had when bought?Try re-seating the ram and try the RAM one at a time.

Also, perhaps you may need to change your CMOS Battery. (the battery on the motherboard)I'm having a little trouble understanding you, but it seems you tried to put ddr2 ram in a motherboard that takes ddr? If that's the case, it wouldn't have fit correctly and there's a good chance you may have shorted the motherboard.it is ddr2 ram that was added and it did fit for some reason which i thought was strange. it has the same 240 pins as the ddr. I will check the battery I thought it was strange that the ram fitted?

I think its strange that when I have the power on with nothing connected it is doing the same it seem power or motherboard problem?Did you put the regular DDR1 back in?yeah the normal ddr ram was put back as soon as noticed was wrong type. I have a feeling its something to do with the MOTHER board. Tested the power unit on another computer and ram all works. My test was to just add the power nothing else and does the same so could not rule out what was causing it. I still need to test the motherboard batery which I hope it is but will soon SEE if not then looks like it will be the mother board thats brokeWhat brand and wattage is the borrowed PSU ? ?
You still may be underpowered...the fact it runs in another rig proves very little.