HELP! When switching on my pc it boots up fine but it opens up My Documents after the desktop page. This only started after I installed Avast anti virus. Everything works fine and I just close down the page it is just a bit annoying. Any help to sort this out is greatly appreciated.

See this:

http://support.microsoft.com/kb/555294

And also as this is often a virus issue:

Please read THIS and after completing the steps outlined post a HijackThis log over in that section along with a brief description of your problem.

Do not post HijackThis logs in this section please.