I'm getting the nasty impression that my choices are extremely limited. We're running on ES2K now, and "management" wants to upgrade. I've searched for ES2003 to buy, but it doesn't seem to exist. The only ES2007 I can find seems to be 64-bit. My servers are most definitely not 64-bit. How can we upgrade our email without throwing out the gear and starting over? Thanks.

You can still buy Exchange 2003, I don't know where you looked, but contact any Microsoft dealer in your neighbouthood and ask them to supply it.