I got a new computer from Computer Lounge at the start of the year and after 9 months of faultless running it has started having some power issues. I've tried to summarise the issue and any testing I've done below:

-I have never been able to get the computer to automatically put itself to sleep or turn the screen off
-At the start of this week it would not start after being put to sleep and then hibernating for the night. I unplugged and left it for half an hour and then when I plugged it back in it started again
-After running successfully for a few hours I put it to sleep again before going to work. When I returned it would not start again
-Unplugging and plugging in again did not help so I left it for a couple of days
-Today I removed the HDD and video card that I had added to the system to ready it for return to Computer Lounge. On a hunch I plugged it back in and it powered up and ran fine for 20 minutes before it automatically put itself to sleep and then wouldn't wake up again
-I reinstalled the video card and HDD and it worked once then wouldn't restart a second time
-I managed to unplug it and then when I restarted it worked again. I created a new power profile that set the sleep time as never and it ran fine for 3 hours. At this point I thought I had it sorted and that the issue was with the power management profile so I shut it down and tried to restart again. No luck.
-Next I tried removing the CMOS battery to reset the BIOS. This let the machine restart to the BIOS but then it would not boot any further than this
-After shutting down it would not restart again.

My concern is that it a BIOS or OS issue and I'm going to send the machine to Auckland to find there is nothing wrong with the hardware. Am I just wasting my time and just avoiding the fact that it most likely to be a stuffed power supply or are there other things I should try?

I have included details of the system below with the changes I requested.

http://www.computerlounge.co.nz/systems/systemdetail.asp?sysid=40&systypeid=2

 

 

 

 

Tek Advanced 

 

Dispatched
12/3/2014

 

$1,149.95  

 

1 

 

$1,149.95 

 

 

 

Change to: ASUS H87M-Pro Intel H87 Haswell LGA1150 mATX Motherboard 

 

Dispatched
12/3/2014

 

$30.00  

 

1 

 

$30.00 

 

 

 

Change to: Intel Haswell Core i7 4770 3.40GHz 8MB LGA1150 

 

Dispatched
12/3/2014

 

$160.00  

 

1 

 

$160.00 

 

 

 

Item: Standard Intel/AMD Manufactures CPU Heatsink 

 

Dispatched
12/3/2014

 

 

 

1 

 

 

 

 

 

Change to: Mushkin Blackline Ridgeback 16GB (2x8GB) DDR3-1866 CL11 (997073) 

 

Dispatched
12/3/2014

 

$170.00  

 

1 

 

$170.00 

 

 

 

Change to: Samsung 840 EVO Series 120GB 2.5" SATA3 SSD (MZ-7TE120BW) 

 

Dispatched
12/3/2014

 

$20.00  

 

1 

 

$20.00 

 

 

 

Item: ASUS DRW-24D3ST Green DVD Writer SATA 

 

Dispatched
12/3/2014

 

 

 

1 

 

 

 

 

 

Change to: Corsair Obsidian Series 350D Mini Tower Case w/Window 

 

Dispatched
12/3/2014

 

$90.00  

 

1 

 

$90.00 

 

 

 

Item: Seasonic SSP-450RT 450W 80Plus Gold Power Supply OEM (SSP-450RT) 

 

Dispatched
12/3/2014

 

 

 

1