How to set the physical path of a virtual directory from the command line using appcmd.exe

 

>\Windows\System32\inetsrv\appcmd.exe set vdir "Default Web Site/MyAppName/" -physicalPath:"C:\MyAppPath"

For more information relating to appcmd.exe and it's various usages, see this link here...

http://learn.iis.net/page.aspx/114/getting-started-with-appcmdexe/

Also to discover which app pool workerprocess is which you can use the following command

%systemroot%\system32\inetsrv\appcmd.exe list WP

or just look at your task manager with the command line column expanded for the w3wp.exe process