Everything has been fine until a couple of days ago. Now almost every time I close a folder or package and move my mouse, I get a message to tell me there is a problem with Windows Explorer and it is closing down. It only takes 2 or 3 seconnds to start up again but it is very annoying.
The problem may have started about the same time as I used a friend's portable hard drive to copy files both ways. I don't know if this has anything to do with it. The drive has now been disconnected.
I may try the startup repair later but it seems drastic since everything else seems ok.
I tried the system restore before only to find that there were no restore points there. This was strange as I have used this before. It may have had something to do with running out of space on the c drive.
Anyway thanks to all for your advice. I will keep trying to fix this problem.