When I switch on my PC the case LEDs light up, the drives sound as if they power up, the Intel P4 screen appears and the fan RPM reduces (this I would expect as it is set in the BIOS), then nothing. It's as if the BIOS is not looking for a boot sequence, I've tried inserting discs in the optical DVD Rom drives and a floppy in the FDD, however the sequence doesn't get that far. I can't even access the BIOS as the POST doesn't start (have tried holding down 'Del', 'Esc' etc as soon as power on). I'm assuming the processor works as I get the intel P4 screen appears, which also indicates the graphics card is ok (ATI X700). I'm also guessing that the BIOS (or at least part of it) is being read as the fan RPM reduces. I've tried resetting the BIOS defaults by removing the CMOS battery, this has an effect as after doing this the fan RPM no longer reduces that the BIOS thermal alarm setting has reset. I'm truly at a loss and would appreciate any help!
Keef66, Already checked that all the connectors, cards etc are snug and they all appear fine. I don't think it's a PSU problem, if there was a problem with any of the supply levels (3.3v, +/-5v and 12v) were not present wouldn't that prevent the drives from spinning up and the graphics card from sending a signal to the monitor? However I'm all out of ideas so I'll take any suggestions!!!!
PSU failures aren't usually noisy, smoky, all or nothing affairs. They often show up as a creeping deterioration in startup, or otherwise unexplained crashes / reboots. I only suggested trying the psu first because it's relatively easy to do if you're able to borrow one. The other things to check by sustitution are obviously the processor itself, the graphics card, and the ram. You ideally need to find an understanding friend with a similar system to borrow bits from.