A 32-bit OS or program can only address about 3.5 Gb of RAM, whereas a 64-bit jobbie can address as much as 192 Gb. Some VSTi's need a LOT of memory--think on the order of 1-2 Gb by themselves. Users are now able to employ multiple high-quality VSTi's--except that they can't with the memory limitation. Hence the need for the 64-bit program, to take advantage of all that beautiful RAM.
HTH,
Richard
My actual laptop runs Win 7, 64-bit, but it only has 4 GB RAM.
Would BIAB function "better" as a 64-bit app? That's what I'm having trouble understanding.