Hi,
there's only one version, and according to your OS, will install as 64 or 32 bit. This said, even when installed as 64 bit (so in the program files folder as opposed to the x86 one), main V5 processes as seen in task manager appear as 32 bit. Read sometime ago that a few things were actual 64 bit components, but can't remember what exactly...I guess a look at process explorer (sysinternals) could tell more.
edit: don't know what I was thinking of, the driver is 64 bit.