Some more Op Shop and eBay purchases..

Today was one of my rare 'free' days, so I decided to do something useful instead of taking off in the car and checking out more op shops. S was working, otherwise we may have done just that, as it is much more fun when there are two of you! However, I was very productive; I vaccumed, washed floors, defrosted the fridge, and fixed this computer...well, I hope I have. Before I started on the housework, I set it up for a thorough ScanDisk, which took about 6 hours, and followed that up with a defrag. The message at the conclusion said there were errors found on the hard drive, which are now fixed. So I scanned these few items tonight, with only one freeze.
At the risk of sounding rather strange, I am going to describe what has been happening to my computer over this past week, and I am keen to hear if anybody can offer an explanation. When I am sitting here typing or reading emails etc., everything is fine for most of the time. But if I move away from the desk, either to put something in the scanner (which I can't reach from where I sit), or go out of the room for even just a minute, the computer freezes. Not just temporarily - I have to turn it off at the button and restart, usually resulting in that awful safe mode screen. It is just like a child - throwing a tantrum when you leave them alone. It is actually quite spooky...am I producing some kind of energy field that interacts with the computer, so it goes off when I move away? Weird...