64 bit version of Microsoft Office

I noticed when installing Office 2007 this morning that there was a folder named something like "64", along with a handful of others for each constituent product. I always thought that Office was only a 32 bit application and it was a long time before a 64 bit version would become available.

Can anyone enlighten me with any more information on 64 bit editions of Office (if they exist), as I can't find much about this on the internet.

SharePoint and Forms Server are x64, and the folder you have there contains select binaries for those applications (even though they may not be installed).

Office 2010 will be available in x86 and x64 editions just like Windows.

Isn't it true that the Office x86 will run in a X64 OS while Office x64 won't run in a x86 OS?

Yes, that's correct - as you can't run a 64 bit application on a 32 bit host.