Let me say that your question does not match your subject.
I run a 32-bit CentOS with virt-manager installed to monitor the virtual machines running on a 64-bit CentOS. That leaves the following:
Is it because I'm running CentOS 5.9 in both cases? Or is it because I performed a full install from a DVD in both cases?
That being said, It's a fact that virt-manager will run on a 32-bit OS.
Thanks, Gene Poole