HP TouchSmart 610-1115uk Randomly Shuts Off Without Warning

i have had this TouchSmart for about 2 years now and it is in immaculate condition. physically apart from dust, which i clean out regularly, you'd be mistaken for thinking it was new. in terms of operation i have always been careful to look after it too, running regular scans of the HDD and hardware, updating drivers and being careful when it comes to what i download.

i have recently upgraded to Windows 8 Pro x64 (within the last 2 months) but didn't do a clean install, i simply upgraded from Windows 7 Pro x64, and to be honest after a few tweaks the computer was working better than ever, it was faster both running programs and in terms of startup time, and graphics looked better than ever.

then about 2 weeks ago it just shut off without warning, not shut down like if you'd asked it to, but just went blank like loss of power, i powered it up and it didn't do it again for quite a while and so i assumed it was a one off. but it soon started doing it regular. i've gone through every thing i can possibly think of trying to diagnose what the problem is, i've checked all wires and connectors, cleaned out all dust and checked for overheating, updated drivers, removed the extra RAM i'd installed not long after purchase, wiped the system and reinstalled Windows 8 from scratch, deactivated Threading on the CPU, and have reduced power to the CPU down to 50%.

this last action did reduce the frequency of the shut off issue significantly but it just seems completely random, i can be running any number of programs and it can work fine for hours, and then i can be doing nothing on it and it will just die.

i have run no end of diagnostics on it and they all say everything is fine, no viruses, no errors and no build up of heat (i've monitored the temperature rise when running and it never gets over 40 now with the CPU power turned down).

the shut off problem seems to occur more often when the computer isn't really having to process very much like when it is left idle or when i'm just using the internet, whereas if i play a game or use a resource hungry application it rarely happens.


please can someone tell me if i'm missing anything, and if i can solve this without HP as my warranty ran out a few months ago, thank you.