Not sure, But why would you want to?

 

pcgeek11

Yes, it is possible to dual boot with both versions.  As far as the operating systems are concerned, it is just like any other time that you install a dual boot configuration.  By and Large, the OS'es are not aware of each other.  Primary limitations are the obvious like not installing to the same partition, making sure that your boot.ini file is correctly configured to allow you to select the particular architecture you would like to boot into, etc.

 

As far as why you would want to do this configuration, at the present time, the 64bit version of vista has some security enhancements around the architecture of the kernel including Kernel Patch Protection AKA Patchguard and additionally has support for higher-end virtualization features such as 64 bit Virtual Server and with VMWare, 64 bit virtual guests.  At the same time, the vista 64bit often has problems with gaming peripheral drivers as many of these have not been updated to 64-bit.