General Program Starting Help.

Hi All.I wonder if anyone in here might be able to help me with something.I am running Win XP Pro with SP3, and all MS Up-Dates etc.But last week I noticed that I could not start nHancer, I also found that I could not start up Vroute and when I went to try and install Windows Media Player 11 again, the install failed.I have removed and re-installed Vroute and nHancer, but this made no difference at all.I should point out that I have not installed or removed anything else as such, except for the new Digital Aviation Fokker.Everything else is running just fine etc, and I have not had any errors from any programs.When I try and start any of these apps, I get the standard Windows error message type oblong box saying it failed to start, and that I should report it to MS etc.I'm just confused as to why this has happened, and would welcome any thoughts on this from any of you as to what your thinking is behind this strange phenomenon.Many thanks in advance for any help with this.