PC is 18 months old, with a clean windows install 4 months ago. No viruses or spyware but over the weekend is now going really slow and today as started shutting down without notice - usually when idle for a couple of mins.
Have deleted most of the programs and software I used but still no difference. Also have checked fans including processor fan and all working fine - any other ideas?
Just a thought Matt,have you checked your processes....just to see if any thing is hogging the system resource's. ctrl+alt+delete....I would guess your cpu usage to be around 4-20%...just a guess though.
I was doing an online a/v scan as Woodchip suggested, but machine shutdown again (just powered down), so I am restarting the scan again.
Although, when I originally restarted the machine, I lost my internet connection again (my network card did not show in network communications box and two monitors on taskbar had disappeared. Unplugged modem, restarted pc and powered up modem 5 mins later and working again now - but how long will my machine last for this time!!!