Microsoft Dynamics CRM, x64 Processors and Virtual Servers
One tip of advice with the recent surge in selling x64 (64-bit) based systems you need to be aware that you can't utilize x64 for your CRM webserver. It's not supported.
Now having your webserver running in 32-bit mode you might be wondering about performance. Being that most of the processing is done on the data tier (SQL Server) you will greatly benefit having your SQL Server as an x64 based system.
With all the above being said there is a blog entry that covers 32-bit IIS on x64. This article isn't really for the faint at heart. It
Although this article can help you get the CRM web server components running on x64 it is NOT supported by Microsoft and isn't recommended at this time.
With the above having two x64 based servers (SQL and Web) this is what we opted to do. Windows 2003 Server R2 (x64) and SQL Server 2005 (x64) SP2 for the data tier. For the web tier I went with Windows 2003 Server R2 (x64; yes 64-bit). The reason I stuck with x64 was due to the growth and continued acceptance of Virtual Servers. The web server is also hosting SharePoint Servers 2007 (x64) as well. For the "virtual server" piece I used Microsoft Virtual Server 2005 SP1 (x64 [64-bit]) and purchased another version of Windows 2003 Server (x86 [32-bit]), called the machine CRM and installed the virtual server to auto-start, installed CRM and connected it to the x64 based SQL Server. This did add to the cost having to buy an additional copy of Windows 2003 R2 but allowed to take advantage of the x64 hardware that was purchased. The end result was a very fast and reliable solution utilizing the x64 capabilities and also the virtual server capabilities available to me.
The key to all of this is choose the proper platform for the proper application. Choose a 32-bit version for the webserver and a 64-bit version for SQL Server.