Over the past few days, my computer has been blacking out and power is still going to the monitor/keyboard as the lights are on but the screen doesn't show anything, and the keyboard doesn't pick up anything. Also, the USB mouse doesn't respond.

When I turn my computer on this also occurs, no matter how many times I restart I still get this.  You here all the fans turn on etc.. but just before the part where an orange light blinks and makes that usual "beep" sound as it starts to turn on, it doesn't quite get there.

After getting annoyed I banged the case at back where the powerbox is and surprisely the orange light flashed and it turned on, though a few hours later it blacked out again. For the last few days I'm hitting it like this to turn it on. Any ideas on what the problem may be?

Don't know if it's the same, but occasionally my monitor doesn't like to do anything.  Unplugging it and plugging it back in makes it work.

If hitting your PSU area makes it work, then I'd assume something fell apart in your PSU. Whatever it is, it sounds internal of the case itself.

rabbit, it's not just the monitor.

Eg, it blacks out. My keyboard has numlock on and scroll lock. Both lights will stay on but no buttons on the keyboard will respond. The monitor is still retrieving power but the light is just blinking which occurs when the monitor is on, but not the computer. My USB mouse optical light is off. And the computer's green light is on, and so are the fans.

By hitting it on the PSU it reboots and starts up fine. I'm going to reformat as I've been meaning to for awhile now, and there could be a very small possibility that maybe some bug has done something, though, extremely unlikely. After reformatting I'll test if the problem is still there, and if so I'll just ring up the shop I bought it from, as it's still under warranty.

[EDIT] Forgot to mention. But when I turn it on, it starts up this way with just the keyboard light(s), computer green light and monitor light flashing and I have to hit the PSU to get it to start properly. So I doubt this could have been caused by a bug, unless somehow it could mess with the internal settings (you get to by pressing 'Del' when booting up) but as far as I know, I always though they were seperate from the computer system and are run directly off the CPU.

Do you have a POST bracket attached to your motherboard?

I can't remember exactly what these are called, but the last three or so computers that I've built have each come with one.  There is a bracket that goes in the back by the expansion cards -- each of mine have come with two USB ports -- and the bracket usually has four lights.  Depending on the sequence of lights that are displayed, you can tell precisely where in the POST (Power-On Self-Test) the boot process is failing.

If the POST doesn't beep then it's not a hard drive format issue.

You should go ahead and open it up, inspect the motherboard, memory cards, processor, heatsink/fan, and expansion cards to make sure everything is seated.  You should try to reseat everything as well, with maybe the exception of the processor (generally I leave a processor where it is unless I really fucked something up when I installed it).

Have you been messing with the voltage settings on your PSU?

It originally happened during sometime I was in the shower. I was on the computer which had been running fine (been on about 5 hours), then I left it to have a shower and as I came back to it nothing was running. I just though it was on standby (despite having explicitly disabled that) and tried holding down "Ctrl + Alt" to no avail.

So my next guess after seeing the lack of power to things was to check the power plug, and I must of bumped the control whilst adjusting it which caused it to turn back on (by rebooting itself :-\). Then it didn't happen until the next day.

I haven't changed the power settings (not even sure how), nor have I changed any computer settings recently (a few months).

The other night when it happened, it wasn't coming back on with the usual nudge. So I took the left side of the case of and checked that all the plugs and such were in properally (which they were). And then plugged it in leaving the side of the case off and tried turning it on. With the case off, nothing I could see wasn't working. After bumping the PSU box (which is enclosed in casing, so I can't see inside it) it turned on. Thus, I'm definite that it's the problem.

I'm not too sure on what the "POST bracket" is, but everything in the case is in the same state as when I last opened it.

Could this have been caused by like surging the power box?, because I'm regularly moving it about and plugging the power in/out about 7-8 times a fortnight. And sometimes the power plugged into it is live.

How old is this? Perhaps it's dying of old age -- the newer products seem to be of horribly low quality.

[quote author=J link=topic=15104.msg153741#msg153741 date=1149314679]
How old is this? Perhaps it's dying of old age -- the newer products seem to be of horribly low quality.
[/quote]
11 months old. (P4 3.2Ghz)

I've had this happen before.
Does your computer use an AGP Graphics card as well as an integrated one on the motherboard?
I beleive it could be caused by the system trying to determine the specified default graphics card.
If this is the case, try plugging your monitor into the integrated graphics card and reboot to see if you can view your bootloader and your BIOS welcome screen. Enter the BIOS and set your default monitor to the AGP card.

I'm using a PCI 16x graphics card. (ATi Radeon X700 Pro) and my motherboard is Gigabyte 915P (GA-8l915P Duo Pro), the graphics card is installed and is running fine, as games like Half-Life 2 are running fine on highest settings.