With all but the SQL Server 7 running side by side on my 64 bit laptop (actually 32 bit SQL 2005 is excluded) I made a guess on this one since the documentation was as listed above.
Historically, it has been my experience that loading the latest version of a Microsoft product first, then reloading the previous will allow side by side configurations. For example, the following Visual Studio versions are running on the laptop... VS2008, VS 2005, VS2003,VS6,and VS5.
And much like the fact that VS6 and VS5 are not supported... they still operate without issues. Others who keep their VB6 and VB5 configurations on separate development machine loaded with Windows 98, as yet, haven't indicated there are issues with anything developed on the 64 bit laptop.
I suspect (not positive), that loading SQL Server 7 on my laptop in a configuration that will run, is possible. 2000 definitely works and is currently working here in a side by side. I can probably dig up the MSDN copy in my library and make an attempt to install it if it is a question.
Given this, might it be conclusive to say that a 32 bit and 64 bit of the same version may have issues but the 64 bit supports 32 so is it actually an issue?
Ah, caveat on the NET versions of Visual Studio. If say a released vs2003 dll is in production, and you develop a newer version in vs2008, the dll on your local will update. It gets tricky. Probably same is true with the SQL versions but they elude me now.