Well after having escaped PC problems for a few months..its decided to return..
My computer is randomly *restarting* this time.
The first thing I thought it might be was temperature,so i downloaded SpeedFan and this is the result:

As far as I can see, all the fans are spinning...so maybe it's not heat? I dunno..
I've run antivirus and anti spuware checks and its all good..
I've made no changes at all and it seemed to have started to happen sinse I got back from my two week holiday..
This is really beginning to irritate me, so any help is greatly appreciated.
I've attached my Dxdiag aswell in case you need it.