It is doing two things, which may not be related. First, it is running incredibly slowly. It can take nearly a minute for Firefox to open, for example. And if you push it too hard by clicking on an item again, that bit of software sometimes just stops running. Everything was working so slowly that I have bought and run Registry First Aid to see if that would help. It didn't.
I thought a virus might be the problem. AVG hasn't spotted anything, though.
It also sounds as thought it's labouring, with a constant low whir. It may help you to know that when I turn it on, up comes the desktop and the little egg-timer icon is on the screen, as usual. It then goes, and then comes back again after about 10 or 15 seconds, so something else is happening.
This is a problem which has happened suddenly, rather than increasing over a period of time.
The other (perhaps unrelated problem) is that when I get a http inn an email, it often starts up Windows Explorer - and then doesn't go through to the web page. I never use Windows Explorer, although it is installed on my PC. That suddenly started to happen at the same time.
This is a repeat of a topic which I posted on the wrong forum. You kindly moved it and it may be that it is already in the queue to be answered but the email I got gave the impression that this wasn't the case. If it is in the process of being answered, please accept my apologies.