I just finished adding support for Vista/Server 2008 on OSSEC. We had some server(manager)-side changes to understand the new events ids and lots of changes on the agent side. If you have any Vista or Server 2008, please help us test it.
You can download the server at: http://www.ossec.net/files/snapshots/ossec-hids-080721.tar.gz
Agent download at: http://www.ossec.net/files/snapshots/ossec-win32-080721.exe
Make sure to update the server first, before the agent. If you find any issues, or if you test and it works fine, please let me know.
*I would also like to thank Chris Buechler for the remote access to some of his boxes to make this possible.