The computer was bought and put together in July 2012, and I've never had a problem with it before now. It has never powered off randomly, not turned on, blue screened etc.
Up until two weeks ago I only had one graphics card and also didn't have the external hard drive. I then bought a second graphics card to sli with the first, and at that time I installed it. I plugged two different power cables into the PSU and connected them to the GPU as I read it's best to use seperate plugs for the GPU. The computer booted up fine and sli was working.
At this time I updated the bios on both my GPU's and that went fine, and then I updated the bios on my motherboard, which seemed to work fine. I then rebooted my PC... and there was no single "beep" sound there usually is when my computer starts. Both my screens were black and it seemed like the LED's were on, the computer was powered, the fans were spinning, but other than that nothing. I tried powering off and on a few times and still the same thing.
I then turned off all power, waited for about 5 minutes and turned it back on – the "beep" sounded and the computer started up fine. I didn't have any problems since then until yesterday and in hindsight should have asked around but just thought to myself that this was just a once off.
Usually, I turn off my computer at night, but for the past few months I've been downloading quite alot due to my download limit increasing so I've left it on day and night downloading, turning it off once a weekish. I also have never really used standby except for maybe once or twice in the past as I've heard it's pointless if you have a SSD.
So last night after I finished playing games I accidently put it on standby. At this point the computer had been on for a few days. So I waited for it to finish going into it's lower power state, and moved the mouse to un-standby it. It started powering up, then just shut down... I was quite confused. I then tried to turn it on at the power, and it had the same problem as a couple of weeks ago – there was no "beep" and I was greeted by a black screen, led's on (keyboard, mouse, headphones and case) and fan's working. However I did notice the HDD led wasn't lit up, but the power was (I didn't take notice of this last time).
I tried to power it off by holding down the power button, and powering it back on a few times and that didn't work. I then turned off power at the psu and tried to turn it on 5 minutes later and that didn't work. I then proceeded to power everything off and wait 20 minutes, and then tried to turn it back on – same thing. I left it on for about 5 minutes to see if anything would change but it stayed the same. I decided to leave it off for the night and wait to the next day.
This morning, I flipped the PSU power on, then powered on the computer... "beep" and it started up fine. At this point I shut it off and went to work.
I would like to know what the problem is and what's going on, and how I can fix it ... I'm terrified my computer is going to blow up
Thanks for your time, and any help is appreciated. If you need any more information please let me know!