EDIT
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I disabled sound in the BIOS, rebooted and it hung.

I removed the (previously) faulty HDD, rebooted and it hung.

I have managed to get my Realtek audio manager open again after its mysterious disappearance.

Subsequently my microphone is now working again, to fix it I had to uninstall audio drivers, disable audio in BIOS, install audio drivers, enable audio in BIOS.

Access via network (with faulty HDD in) seems to not be triggering hangs at the moment.

I think with the sound problem fixed it might play a little nicer, but I think its still going to hang.

If it does, then I'm fairly sure its been narrowed down to the mobo.

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EDIT
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Pretty convinced my motherboard is the culprit, because nothing else seems to have any obvious problems (bar the hard drive, which the PC still hangs without it being plugged in)

So thank you all for helping, once I get more rep ill up a few of the answers.

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My PC is doing some weird things...

Sometimes when I open up a program, lets say Adobe Photoshop, it will load everything normally, nice and quick no problems and I can use it fine.

Other times its a little odd, and it loads the program as if it's only using half of the CPU. It's pretty obvious when it does it, normally the loading screen skims past, but when it does this weird load you see it slowly tick though each thing, and the program itself becomes incredibly slow. Even Google Chrome does it sometimes.

Yet when I exit and reopen the program without doing anything else, it typically opens fine without lagging.

I think this problem is probably a symptom of something bigger, because of other problems I'm having.

Random hangs; no matter what I have open or what I'm doing. My PC will sort of freeze up for a few seconds. If music is playing it will either loop the last second or two, or it will buzz. This only lasts for a few seconds then it returns to normal without having to restart. During this time all programs lock up and freeze, and the mouse and keyboard are useless.

I am also having a weird issue with my audio jacks, without touching my PC at all, sometimes I will see a popup saying that I have unplugged something or plugged something in, neither of which has actually happened.
Pretty sure this is cause by the motherboard.

I recently had a 'Pink Screen of Death' (yes pink) which pointed to my audio drivers.

The lockups seem to happen with some consistency when someone is accessing my shared files via my home LAN.
Which leads me to believe either one of my hard drives is acting up or more likely the controller.

One of my drives had a bit of a crash before, I used Spinrite and managed to recover my stuff and now the drive appears to be working okay.
This is possibly adding to the problems.

My best guess is something has gone wrong with my motherboard, possibly a power issue or a chip has died, I really don't know.

So what I would like to know is:
Have I have missed some obvious diagnostic to help figure out what it is, 
or should I just bite the bullet and assume its my motherboard acting up and buy a new system?

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dxdiag[64-bit] - <http://pastebin.com/G30kb2TL>

PSOD (minidump) - <http://pastebin.com/aZsv0H56>

HWiNFO64 (system info / specs) - <http://pastebin.com/X6h3K8g6>