Before I take it to the shop, any advice?

[Adrian]

The other computer won't start. It was taking a long time to start, frequently needing to be turned on and left for minutes and then off and on quickly before it would work, but now it has stopped altogether.

Lights come on, drives make sounds but it does not boot at all. I have removed the battery and left it out overnight and fitted a new one, but this makes no difference. I cannot see that anything has got loose from anywhere.

Any ideas of what might be wrong?

[Diver300]

Remove anything that isn't vital, such as all disk drives except the one with the operating system, fancy graphics cards (as long as you have onboard graphics so that you can see what is going on) and any memory over one stick.

If it still doesn't boot, you can only test by substitution.

[fred the great]

Sounds like the OS is corrupted. Try a reinstall using a boot disk made with another Computer. Of course the OS on the boot disk should be the correct version!

Otherwise you will have to reformat and lose your files

[rusky]

Do you see the BIOS screen or is the display blank? Are there any beeps when you power it?

[nuttycyclist]

The big test would be whether you can boot the machine off another medium, e.g. a live CD (BartPE or Trinity Rescue Kit or Ubuntu (links ->  List of live CDs - Wikipedia, the free encyclopedia) )

If yes then it's the operating system/hard drive, if no then it's the hardware.

[Adrian]

No BIOS screen and no beeps but it does sound as though it is trying to access the floppy disk drive etc.

[rusky]

Possibly the PSU or something on the PC. Do you have another PSU to test with?

[Adrian]

Alas not. The shop beckons. Thanks for all the help thus far.

[Adrian]

Apparently it was a power supply problem. There was power to the motherboard but it was insufficient.

Thanks again

[rusky]

Apparently it was a power supply problem. There was power to the motherboard but it was insufficient.

Thanks again

God I'm good!