Microsoft has released two different versions of Exchange 2007.

Exchange 2007 32 BIT
Exchange 2007 64 BIT

The Exchange 2007 64 BIT does have a subset i.e.

Standard Edition
Enterprise Edition

For this article I will only cover differences between 32 BIT & 64 BIT.

Some of you might be wondering this is absolute rubbish & I am not too surprised either. Simple reason being I have recently come across a few engineers who were so sure and simply would not agree a 32 BIT version exists.

So lets look at some differences.

Before we go any further click here to download the 32 / 64 BIT version from Microsoft website.

Note:The first and most important thing to keep in mind is Excahnge 2007 32 BIT version is NOTsupported by Microsoft in a production enviroment.

Exchange 2007 32 bit
Exchange 2007 64 bit
Not Supported in a production environment.

This is the only version which is supported by Microsoft.
32 BIT Management tools can be deployed to manage  a production environment running on 64 BIT versions.
Fully supported in a production environment.
The schema can be upgraded using the 32 BIT version.
Fully supported in a production environment.
SCC + CCR can be used for testing purpose only in a non production (LAB) environment.
These are enterprise edition features but do work in this version.
Fully supported in a production environment.
Unified Messaging can be tested in a non production environment.
Fully supported in a production environment.
This version can NOT be purchased from Microsoft OR Microsoft partners.
This can be purchased through the normal Microsoft channels.
No Trial License keys are required
License keys will be provided when the product is purchased.
Automatic spam updates don’t work in this version.
Can be updated using Microsoft Windows Updates.
Available editions:
Exchange 2007 32 BIT Standard edition.
Available editions:
Exchange 2007 64 BIT Standard edition.
Exchange 2007 64 BIT Enterprise edition.
Storage groups and databases: You can have a maximum of 5 databases per server in as many as 5 storage groups on the 32-bit version.
Note:This limit is also applicable on X64 BIT Standard Editions)		 Storage groups and databases:  You can create a maximum of 50 storage groups on each Exchange 2007 server, with up to a maximum of 50 databases.
This SHOULD NOT be used as a edge Transport server either as it is considered as a production environment
Fully supported in a production environment.

I personally think this is an absolute excellent option for customers to test this product and get a feel of it before going ahead in a production environment.
To give it a thought you can always use an old server which is not currently utilized to have a play with the 32 BIT version which will bring you up to speed & without impacting your production environment.
You can also test power shell scripts & gear yourself before hand for your move over to Exchange 2007. The same scripts can be edited as necessary and re utilized if your LAB domain does not reflect the production environment. For example:
LAB Domain: Lab.local
Production domain: abc.com

Note :