Hi, I dont really know what screwed up, but I build a tower pc and installed ubuntu on it and it was working fine. I thought I would try out arch linux, and so started to install it however, the power accidently got turned off half way through. After this the pc would not start - no lights, nothing. I held the start button in for a while with no power and then turned the power back on.It came on, so just to play safe, I re-installed ubuntu and it was working ok. I only get to use the pc occasionally as I dont have elecricity, I live in a truck and normally use a laptop. The other day I went to use the pc and nothing. It wont turn on, and is as dead as a do do. If I hold the start button in for 30 seconds the fan on the cpu starts to spin for about a second and then nothing, no lights or anything. Does anyone have any ideas pls? Have I screwed my motherboard up, by the installation being aborted? Many thanks if anyone can give me some ideas to try next time I get to use the pc.

Certainly doesn't sound like anything software could do. More likely the motherboard was damaged due to a power surge before or after the power went out. Was the computer connected to a surge supressor?

No it was just plugged in to normal power supply.

yes this happened to me way back open the case pull the ram chip then put them back in.
This will cause bios to go back to day one. This is a hardware problem and if it keeps happening it will be time for a new video card or ram chips. you see the first things bios does is look for the display card ram then ram. so if you have that no light thing. make sure the power supply if in USA is set to 110 and then check plug.
Let me know. on many pc HP Dell etc etc. the power surge will cause bios the rom chip to become let's say not inline.

When you disconect the ram chip or computer bios clock battery it will take all the current away from bios. the Read only memory (ROM) on the the mother board and the ROM chip on the display card will go back to oem.

Now when we boot the processor the ROM chips will go back to OEM state. You will need to reset the time and date.
If this does not work you have a power supply failure that does not mean the actual unit but a bad supply of current.
let me know.
Let me know

Thanks a lot. The next time I get to use the pc I will try this and let you know what happens. It actually was not a power cut as such, its that my mate pulled the extension lead out by mistake. Im going to his house where I use the power in a couple of weeks so I'll let you know then, thanks.

Try to boot to BIOS setup and see if it has any strange power-up button settings (assuming you can get it to boot).
This sounds like an option, my machine has this same delay for recognizing power-off.

Write down all BIOS settings, some may be custom set for your hardware.
It is a good idea to have this set down on paper for emergencies.
Some of these BIOS settings may be wrong, or there may be other values in CMOS that you do not see. The assumption here is that this is due to clobbered BIOS CMOS settings.

To reset CMOS:
Find user manual, find the CMOS battery backup jumper.
Remember where the jumper is, you have to put it back afterwards.
<TURN POWER OFF>
Touch one hand to some ground, like the power supply case.
You do not want to kill the whole thing with a static discharge.
Pull jumper, (I use medical clamp, they are impossible to get with fingers), and reinstall sideways on one post, not connected
(so as to not lose it, and to mark the old position).
Wait a couple minutes for CMOS to forget everything.
Put the jumper back where you found it.
You will have standard BIOS settings as from the motherboard factory, but may differ from tower builder choices and may need hard-drive settings (at least to select boot device).

Maybe, a broken install could do this because some of the new hardware button controllers intercept button pushes, thus there must be a mechanism for telling BIOS to pass button push to udev or other Linux program. It that is the problem, then must find a udev control file in Linux. If you did not clear the directories before reinstalling, the it could still be there messing with the other Linux.
Search the /etc directory for any file that has a date out-of-place for the current installation. Check to see if it is from the current Linux installation by looking at the included files from the distribution docs.
Safer to clean the /etc and /share (by wild guess) directories and reinstall whole thing, unless you know how to do partial install for that distribution.