I just bought a new computer with Windows 7 (64 bit) and Poser 8 runs fine without having to set the compatibility to WinXP.  I just checked the Windows 7 compatibility website and searched for Poser.  It lists that Poser 8 will run, which it does for me, but they are working with Smith Micro on Poser 7.  I didn't try P7, but thought about installing it until I saw that it supposedly isn't compatible.

The W7 website didn't mention P5 or 6.

Poser 2, 3, 4, 5, 6, 7, 8, 9, 10, Pro 2014, 11, 11 Pro