Edit the script, C:\Inetpub\AdminScripts\Adsutil.vbs. Change this line:
IsSecureProperty = True
to:
IsSecureProperty = False
Now you can find the IUSR account password by using the Adsutil.vbs tool. Open up command prompt and navigate to C:\Inetpub\AdminScripts. Run either of the following commands:
cscript.exe adsutil.vbs get w3svc/anonymoususerpass
cscript.exe adsutil.vbs get w3svc/wamuserpass
to display the IUSR and IWAM account passwords respectively.
via How to get the IUSR and IWAM user account passwords on an IIS server | JasonSamuel.com.