jfhoff: I feel it's important to note that there is no "magical" benefit in switching to another development language for this task. All 32-bit programs - regardless of language - are subject to the 2gb limit on Windows. That's a Windows limit, not a VB6 limit.

If you were to switch to a language with 64-bit support, that is a different story, but then you would be limiting your client base to users of 64-bit versions of Windows, only - maybe this is acceptable to you, maybe not. Something to think about.

If you are serious about writing a Bitcoin or Bitcoin-like client, you'd be better off investigating ways to offload the calculation work onto the GPU instead of the CPU. (The parallellism of bitcoin-type calculations makes this a MUST if you are serious about building your own client.) Among other benefits, assuming you are familiar with GPU programming, that would allow you to tap into much higher-bandwidth GDDR memory, and if you could pool both video RAM and regular RAM, that would help.

At the end of the day, though, you'd really be better off with some kind of hashing system that would enable you to reduce the program's memory consumption needs. Regardless of development language, you generally don't want to be monopolizing more than 2gb of RAM. I would investigate how various bitcoin clients handle this, because unless you want to limit yourself to a very small number of users, the 2gb problem is something you will eventually need to solve.