This is not a question but a solution that took me about a month to find. Consistently found Alt Tab to change programs would not work, and when I hovered over the taskbar at the bottom of the screen, the postage stamp image of the application would flash on once then disappear. Sometimes I could just not get an open application to maximise.
Usually use my HP laptop at a workstation but when using it in another location noticed the problem had disappeared. Figured there was something about the workstation. Tried back at the workstation and through a process of trial and error found it was a Logitech Skype USB Speaker Phone. It is a fairly old model - maybe 2007 - which I got as a freebee when I purchased a PC. It doesn't seem to like Windows 7. Unplugged it and there is no further problem.
Hope this helps someone else.