As far as I know, Aero is not yet supported. You can check the following thread to see the discussion about it: http://forum.parallels.com/showthread.php?t=31161
That Aero is still not available more than 7 months after the release of Parallels 4, that, I knew already. I very well understand the difficulties you might have to try to get it working within the "Coherence" hack. Yet it would be perfectly USEFUL to your customers (and I'm one of them with multiple licenses - me and my team members) if you released that support, be it limited and only available in windowed or even full screen mode. Having XP running in a VM is fine, but it also is close to be a 10 years OLD product. Proper support of Vista and upcoming Windows 7 is very important for developers teams using Parallels to boost their multi-platform developments and testing. As well as for customer support teams.
