<p>I'm by no means a sysadmin so please correct me if I'm wrong.</p>

<p>I want to run aspnet_regiis.exe -s.
This requires the metabase path of my website.</p>

<p>How do I find this metabase path?</p>

Just run aspnet_regiis.exe -lk to see a list of the registered applications, their metabase paths and the version of the .NET framework installed for this application.
Also, here are a couple of links that you can use to find the metabase path:
http://msdn.microsoft.com/en-us/library/ms524682.aspx
http://www.windowsdevcenter.com/pub/a/windows/2005/10/25/hacking-iis6-with-metabase-explorer.html
http://www.codersource.net/csharp_iis_metabase.html
HTH,
Don