NETSTAT -ano showed Skype (via the PID) was using port 80.
This was preventing IIS starting a local website with the message:
The process cannot access the file because it is being used by another process. (Exception from HRESULT: 0x80070020)
This was resolved in Skype by unchecking Tools > Options... > Advanced > Connection > "Use port 80 and 443 as alternatives for incoming connections"