While you have to run Exchange 2007 on 64-bit hardware in a production environment, you can remotely manage Exchange 2007 from a 32-bit client running the management tools.
You can download the 32 bit version of the management tools here. There are supported on Windows Server 2003 R2, Windows Server 2003 SP1, and Windows XP.
It is in fact a good idea to design this in at the outset as there is at least one feature that requires a 32-bit client in the forthcoming SP1.
Mark Arnold points out that if you want to export a mailbox directly to a PST then it needs to be done on a 32-bit machine.
Once you've put the data into a running store you can then do the export out of that store. Use the PowerShell command below:
Export-Mailbox -Identity firstname.lastname@example.org -PSTFolderPath C:\PSTFiles\jsmith.pst
There is, however, one stinking huge monster of a problem. The PST has to be done on a 32bit machine and it has to have Outlook 2003 or 2007 installed on it.