I think I caused this myself and I don't think I have a virus (although, of course, I cannot be sure as I cannot run my virus checker, apart from Spyware Doctor which doesn't detect anything). Anyway, I was downloading the free version of AVG and removing the trial version when things went wrong.
I have also tried to click Start, Run and type Command but that won't work either.
Some programmes take me to a web page called Microsoft Windows File Associations but to be honest I don't know how to find what extension I am meant to be looking for.
rundll32.exe is mentioned when I click on some programmes. I have got HiJack this but it won't launch.
I hope someone can help and I apologise if this has been addressed before.
Best wishes. Colleen