I have used this before, but be careful. Make sure your Exchange Server Groups are in the default location. I seem to remember bad things happening if you had moved them somewhere other than the default (users) OU.
RecreateDefPol.exe is a tool developed for the restoration of the Default Domain and Default Domain Controllers policy files, in case of accidental deletion. This tool is for use exclusively on Windows 2000 Server, Advanced Server, and DataCenter Server. Do not use this tool on Windows Server 2003; use Dcgpofix.exe instead (included in Windows Server 2003).