IIS Backup w/ OS re-install

I work for a smaller hosting company and am in charge of a recovery plan for our web servers. All documentation suggests that you can use the IIS configuration (Metadata) backup to recover from IIS meltdown, excluding an OS re-install. My question is how can I recovery the several hundred virtual directory mappings for all of our web sites in the event of a complete OS re-install. I can successfully back up and recover the wwwroot datafiles. When I try to restore system state back up it corrupts IIS.

I hope you have the answer! Thanks!