I found while looking for a running program in Task Manager that the CPU usage was at a steady 100% There were about 8 little programs running so I ended all those so nothing was running but the CPU remained at 100%.
About a minute or two later my screen froze solid which it has been doing quite a lot recently but I haven't noticed the CPU - perhaps 100% has always been there and indicates the problem. Once it froze on boot up.
Yes I have Ad-aware and Spybot which I always update and run. Windows Defender Beta 2, no - I shall look into it.
After that scare I seem to be OK.
SG Atlantis - a very good question. As there was nothing running I didn't think to look for any other process using the CPU though there must have been something. I was too concerned about shutting down quickly before it blew up. If it happens again I shall be more inquisative.
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