It's been a while, but finally I had some time for a new post.
In my post "Vista #7: Software part 4", I mentioned the problem I had with installing SP1 for VS 2005. A few weeks later, the SP1 came with the windows update and installs correctly. After the installation I also installed the SP1 Patch for Vista.
Finally my VS2005 is up and running. But when starting VS2005, I always got following message

When pressing the continue, VS 2005 starts up. After a few quick checks it seems that VS2005 runs normally without any problem. Trying to disable this warning, I set off the UAC, change the startup of VS2005 with admin rights, but nothing seems to help.
My guess is that it's just a warning to be sure that you have enough rights for using VS2005.