This is probably old news to a lot of people, but I just ran into an error message in IIS7 on my Vista saying that "The process cannot access the file because it is being used by another process" whenever I tried to start my default website.
Ah well, I thought...Better shut down various other applications although I was wondering what file it could possibly be that there was a sharing conflict on. So, all other app's seemingly shut down, but I still couldn't start my website.
Before I got the error I had been spending numerous hours getting more and more annoyed at IIS7 so I concluded that this was probably something caused by yet another pseudo-paranoid default security setting somewhere - and I guessed that the error was probably misleading and in fact not related to files at all.
Luckily at this point Ruwen came to my rescue and pointed out the obvious that I somehow had missed:
Ruwen: "it could be skype blocking the port 80"
And it turned out that he was (as always) right. Skype listens by default on port 80 and thereby blocks the device (LISTEN on 80) that IIS is using when starting a site.
After visiting Skype's advanced settings and turning off that obscene feature saved my day.