Trouble booting PC and random crashes

Hi,
I get the following error messages when booting my PC:
Me Fw Downgrade request mespilock Failed and error sending end of post message.
I press the power button on my PC and sometimes it will instantly power on and off again. Sometimes when I press it the power comes on for a few seconds and then reboots itself. Sometimes it will power on and then I just get a black screen. Everything is powered on i.e. fans, monitor but the PC doesn't boot. I have to power off and on again. This usually happens a few times before the PC tries to boot and then it either goes to windows or I get the above error messages. Once I get the error messages a further reboot usually makes the PC go to Windows. The longer the PC is left unused, the longer it appears it takes me to boot the PC for some reason. Once I get it to boot and then turn it off it will probably reboot straight away but if I leave it off overnight I have the same problems in the morning.

Lately it has just started to reboot itself whilst I have been playing games.

Is this a virus, a hardware issue or a software issue do you think?

Computer Type ACPI x64-based PC
Operating System Microsoft Windows 8.1 Professional
OS Service Pack -
Internet Explorer 11.0.9600.17801
DirectX DirectX 11.2
Computer Name STEVE-PC (Home)
User Name Steven
Logon Domain STEVE-PC
Date / Time 2015-06-03 / 23:26

Motherboard:
CPU Type QuadCore Intel Core i7-4790K, 4200 MHz (42 x 100)
Motherboard Name ASRock Z97 Extreme6 (2 PCI-E x1, 3 PCI-E x16, 1 Mini-PCIE, 2 M.2, 4 DDR3 DIMM, Audio, Video, Dual Gigabit LAN)
Motherboard Chipset Intel Wildcat Point Z97, Intel Haswell
System Memory 16338 MB (DDR3-1333 DDR3 SDRAM)
DIMM2: Kingston HyperX KHX2400C11D3/8GX 8 GB DDR3-1333 DDR3 SDRAM (9-9-9-24 @ 666 MHz) (8-8-8-22 @ 609 MHz) (7-7-7-20 @ 533 MHz) (6-6-6-17 @ 457 MHz)
DIMM4: Kingston HyperX KHX2400C11D3/8GX 8 GB DDR3-1333 DDR3 SDRAM (9-9-9-24 @ 666 MHz) (8-8-8-22 @ 609 MHz) (7-7-7-20 @ 533 MHz) (6-6-6-17 @ 457 MHz)
BIOS Type AMI (08/05/14)
Communication Port Communications Port (COM1)

Display:
Video Adapter NVIDIA GeForce GTX 760 (4 GB)
Video Adapter NVIDIA GeForce GTX 760 (4 GB)
Video Adapter NVIDIA GeForce GTX 760 (4 GB)
Video Adapter NVIDIA GeForce GTX 760 (4 GB)
3D Accelerator nVIDIA GeForce GTX 760
Monitor LG IPS234 (HDMI) [23" LCD] (210116843009)

Multimedia:
Audio Adapter C-Media CMI8788 Audio Chip
Audio Adapter nVIDIA HDMI/DP @ nVIDIA GK104 - High Definition Audio Controller
Audio Adapter Realtek ALC1150 @ Intel Wildcat Point PCH - High Definition Audio Controller

Storage:
IDE Controller Intel(R) 9 Series Chipset Family SATA AHCI Controller
Storage Controller Asmedia 106x SATA Controller
Storage Controller Asmedia 106x SATA Controller
Storage Controller ASRock RAM Disk
Storage Controller Microsoft Storage Spaces Controller
Disk Drive BUFFALO HD-PVU2 USB Device (465 GB, USB)
Disk Drive Crucial_CT512M550SSD1 (512 GB, SATA-III)
Disk Drive KINGSTON SV300S37A240G (240 GB, SATA-III)
Disk Drive ST3000DM001-1CH1 SCSI Disk Device (3000 GB, 7200 RPM, SATA-III)
Disk Drive ST3000DM001-1CH1 SCSI Disk Device (3000 GB, 7200 RPM, SATA-III)
Disk Drive ST3000DM001-1CH166 (3000 GB, 7200 RPM, SATA-III)
Disk Drive WDC WD20EARX-00PASB0 (2000 GB, SATA-III)
Optical Drive ATAPI iHAS124 B (DVD+R9:8x, DVD-R9:8x, DVD+RW:24x/8x, DVD-RW:24x/6x, DVD-RAM:12x, DVD-ROM:16x, CD:48x/32x/48x DVD+RW/DVD-RW/DVD-RAM)
Optical Drive HL-DT-ST BDDVDRW UH12NS30 SCSI CdRom Device

 

Here's a 2 page thread from 2011 with no solution for that error
http://en.community.dell.com/support-forums/laptop/f/3518/t/19403065?pi239031352=1
There are links in the thread showing it does not just occur on Dell computers.

 

Yes. I had already read that article when doing a Google search on the problem. It does suggest a malware issue could be the cause. Perhaps you could help me eliminate this avenue please?