The last week or so my PC has decided to switch it off on daily basis - today it has been particularly bad. Funnily enough today my hayfever was uber bad too, so I think my PC migt have a hayfever or something. 

Basically it just switches itself off while I am playing League of Legends, so not a very demanding game, but you HAVE to fucking participate, and when it switches off and I have to waste 3 minutes getting back in it sets me back a lot. 3 times in one game has really pissed me off. I thought it was a problem with the PSU fan so I moved it higher up and closer to the window, as well as turned on a rather large fan to ventilate the room properly, and pretty much pointed it at the processor. It still continued to do so, so I thought it was a problem with the power supply, so I changed the sockets around, the extensions etc, moved some stuff up and about. It still dies, now it's completely dead. Won't switch on AT ALL. Before it proceeded to kaput I have checked the temperatures and they were in range of 40C, with about ~1000 RPM of the fan.

I've also proceeded to open it and check out the insides, as well dust around a little bit to see if maybe the fans were blocked, as well as checked the connections and made sure that the wires were properly connected.

So the components I have include; GTX 550TI, INTEL I7-2600K / 8GB DDR3 .

Your PC is tired of playing sissy games and wants you to start playing DotA 2. =)

:P

Wish I could help more..

That's what pisses me off even more. Lol is not that fucking demanding! So why it struggles is beyond me..

What was your username there? I think I played with you .

I had similar issues with my PCs before. One time it was the power supply slowly dieing, another time the CPU fan was broken and a third time the thermal paste on my CPU was flaky and needed to be exchanged.

Even if the sensors tell you that there are no heat problems there can be hot spots that force the automatic shut down, if there is sth wrong with the thermal compound like in my last example.

Sounds very much like a PSU-problem, is the PSU questionable quality? Is it old? Does it provide enough power for your setup?

They eventually all go bad, the cheapo ones fast especially. Nothing u can do but get a new one.

Could also be the CPU overheating and the computer shutting itself down to protect it from damage. Do you have overclocks and a stock fan?

The PSU I got was pretty damn cheap, so I think it's really down to the PSU throwing the towel in already, yes it is that shit. But there is warranty etc on it, so I'll likely try to get it to them so they can fix the problem as its their fault that the PSU they've provided cant pull more than a month.

Fucker came on for about 30 mins, then switched off again. Now refuses to power back on. Yes, I think it's definitely the PSU playing up, but the thing is.. I haven't overlocked it or anything, so that's what confuses me, the tests that I put it through are NOT demanding for the specs that it has to actually shut down like a little bitch like that..

You've already checked the right things, not much anyone can say without being there in person. Trying to replace each part one by one until it's fixed is the best way unfortunately.

I warned you about the PSU man.

It definitely sounds like it can't supply all of your components with sufficient power and it just decides when it wants to work. You can try re-seating the CPU and CPU fan too, but I don't think that's the issue.

A Corsair 500w+ will do you nicely as a replacement.