There shouldn't be any problems running it (there are a lot of programs that are being used on 64-bit systems that are only 32-bit), but your partner is correct that a 32-bit program won't be able to access as much memory as a 64-bit one can.

If you've got more than 4 gb of RAM on your system, and you intend to render in Poser, than Poser Pro 2012 is the better option.

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If you're joking that's just cruel, but if you're being sarcastic, that's even worse.