Vcenter 5.1 compatible with Windows 2008 R2?

Hi,

I'm puzzled a bit; I've tried installing vCenter 5.1 and 5.5 both on Windows 2008 Datacenter R2 with a fresh install of the OS.  Both times it has choked.

Am I missing something?  Is vCenter compatible with the 2008 R2 Datacenter version?  I have 5.1 running on a VM under Windows 2008 R2 standard.  ?

Thanks!

--Ben