, cheong wrote

*snip*

Not exactly. Any 32-bit applications can get full 32-bit range of address space in 64-bit environment, if the machine have more than enough RAM (It's not that they can't have that in 32-bit machine, but some of the memory content will be on disk then, and this could mean a performance hit).

This fact can be useful for applications made with out-of-proc COM+ components.

That fact is even more useful to in-proc COM objects. 32-bit apps also have a 32-bit heap, which means even if you're using a scripting language like VB, you're still constrained to using less than 3GB of total memory in the address space, whether those objects are VB variants or not. If you're 64-bit you can have more VB variants in your address space.