First I wanted to know which version of IIS is installed on the server. So, I got the following from here.
You can look at %SYSTEMROOT%\system32\inetsrv\inetinfo.exe. Right-click and get properties, click the Version tab.
The IIS version in my case is 6.0.3790.3959.
Now I also want to know If there are any patches installed for IIS. If yes, how to view them as a list?
Run a command prompt with admin rights and try this one:
You could pipe the results to a file and then parse by the KB number for comparisons.
As far as I can find on Google is that there's only 1 IIS patch(Web DAV security patch) (targeted directly at IIS itself) released in 2004, if you have updated using Windows Update since 2004, you should have that patch.
Most other components are usually stand alone and are either a part of .net or other CGI/FCGI/ISAPI component which are not counted directly as IIS.