I recently installed Railo and when I tried to set it to port 80 it failed and after asking around I found that Skype had a hold on that port, closing Skype and all was fine.
I recently installed a local version of ColdFusion. Setup a new website to run https on port 443 and got this message when IIS tried to start the website.
the proces cannot access the file because it is being used by another process. (Exception from HRESULT: 0x80070020)
I immediately thought of Skype again, I closed Skype and started the website fine after that, seems Skype had a hold on port 443 also.
So if your having issues starting up web servers on port 80 or 443 trying closing Skype first.
PS: Skype still works fine afterwards, it must find different ports to use.