In reading through comments regarding Exchange 2007's lack of 32-bit support and confusion around why Microsoft decided to provide a 32-bit "test" version of Exchange 2007, I thought I'd offer some facts about this version and some possible reasons that Microsoft went 64-bit-only with Exchange 2007.

First, as advertised, the 32-bit version is for testing only. Many people like to test server software in a virtual environment before making the production plunge. Take note that Virtual Server 2005 R2 does not support 64-bit guests virtual machines. Even VMware ESX 3.0 only had experimental support for 64-bit guest operating systems. ESX 3.0.1 now includes full support for 64-bit guests, but this is a recent release. Sure, desktop virtualization packages have supported 64-bit guest OSs for a while now, but the enterprise-variety virtualization offerings are just catching up to this.

In short, had Microsoft opted to skip a 32-bit testing version, they would have locked out anyone who wanted to test the product on older servers -- those that do not support 64-bit. I don't think that releasing a 32-bit unsupported test version was irresponsible and it shouldn't be confusing. It's for testing, runs on just about any hardware you have laying around and is easily available.