I've got 2 64-bit servers for the Mail Box and Client Access, but my domain controller is 32-bit. Can I install Exchange 2007?
Yes, all of the commands should be run from the 64 bit system that you are installing exchange on. You must be a member of the Schema Admins group as well as the Exchange Admins group to do the AD prep work. If you are running the schema dn forest updates manaully they still need to be run from the exchange server and you still need the appropriate permissions to modify AD