Had this happen today.

Tried to install WordPress on a Server 2008 box and the install just hung on step 1 of 7 Installing Update for IIS 7.0 FastCGI (KB980363)

The problem is it attempts to run
net stop iisadmin

and if there are other services installed that depend on that (like smtp) it will wait indefinitely on the prompt asking if you want to stop those dependent services too.

The solution is to manually run
net stop iisadmin

then find net.exe in the task list and end process (if you are still letting the webpi install run).

You'll note that cancelling the webpi install also hangs. kill net.exe works for that too.

Best way is to net stop iisadmin yourself before running webpi.