The links in Joeqwerty's answer are excellent. The first link describes resetting the IIS virtual directories for OWA. This might be worth a shot, since they don't look like they will take very long, but I would not be hopeful. From the second link ..
If you have to reinstall IIS on the
server that is also running Exchange
2000 Server or Exchange Server 2003,
you have to reinstall Exchange Server
at the same time.
An alternative is to rebuild the server from a backup before the removal of IIS, then put back the current mailbox and public folder stores. Not sure if this will be less work than re-install of Exchange, but I expect it is more likely to get all of the configuration details set properly.
I hope you learned something about taking proper care on production servers ...