If you are running OCS 2007 or 2007 R2, do not install the patch KB974571. This patch is known to break OCS 2007 installations. In cases where the Office Communications Server 2007 has this patch, you will not be able to install the server and will get an weird error saying that the time is not correct or not in sync.
Here is the Microsoft KB article about this error.
Let me know if you have installed this patch and are able to run your OCS 2007 server without issues.