i have just built a new pc for a friend but there is a really wierd problem when i try to start it up. when i press the power button 1 of 2 things happen:

1) you hear the pc power up shortly followed by a single beep then you hear the hard drive whirring and the pc starts up like normal and works perfectly normally.
or
2) you hear the pc power up and then nothing, no beep, no startup, nothing it just hangs there. the only thing that you can do is turn off the power at the socket and start again.

now if that is not weird enough it seems to happen completely ramdomly no matter how it was shut down or started up.

i have no idea what the cause is and would welcome any suggestions.

Hi and welcome to D-A-L

check all the connections, make sure everything is seated properly eg RAM, Graphics Card, Sound Card

sorry for the delay been on holiday
i have tried what you suggested (opened the pc and tripple checked that all cards and connections where firmly in) but the problem is still there
any other ideas on what it could be?

The fact that there is no beep code at all means that it is not reaching the POST (the system self-test before it tries to detect drives and find an operating system). A RAM error would normally cause a beep code - so it's probably not getting that far. That leaves you with a relatively small number of possibilities. Depending on whether you have any spare parts available, I would troubleshoot it in the following order:

1. Try a different CPU
2. Try a different power supply
3. Swap out the motherboard (or run extended tests with the CPU and power supply in a different system.

Also, double-check voltage settings, speed settings, etc. in the BIOS. These are usually auto-detected but you might find that the settings are slightly wrong and sometimes it upsets the POST process.

Hope that helps

Thanks alot i dont have any spare parts here at the moment but i can get some soon to try these new tests.
i have not swaped out a motherboard or cpu on a system that has already been set up before. will i have to format the hard drive and start it all from scratch again?

That's a good question. If you change the CPU or the power supply, then no - you won't need to re-install anything in Windows.

However, if you change the motherboard for a different model, then it is likely that there will be different drivers to install. If the hard disk controllers and/or on-board graphics chip are different, then Windows will probably not boot at all. The disk controller problem can be avoided by uninstalling the drivers for it before you shut the PC down to do the motherboard swap. At least, that's what I've read from a reliable source in the forums here but I've never tried it myself. Also consider that, if you're running Windows XP or Vista, you may need to re-activate Windows when it detects that you have significantly different hardware installed. Whenever I'm troubleshooting hardware, a motherboard swap is always a last resort.