Systems that have changed the default Access Control List permissions on the %windir%\registration directory may experience various problems after you install the Microsoft Security Bulletin MS05-051 for COM+ and MS DTC
On a computer that is running Microsoft Windows XP, Microsoft Windows 2000, or Windows Server 2003, one or more problems may occur after you install the critical update that is discussed in Microsoft Security Bulletin MS05-051
http://support.microsoft.com/default.aspx/kb/909444