When installing Dynamics NAV 2009 one of my friend’s rune into this problem:
Microsoft Dynamics NAV 2009 Build 27808
Microsoft Dynamics NAV 2009 RoleTailored client
Fatal error during installation.
Could not open key: UNKNOWN\MSComDlg.CommonDialog.1\CLSID. Verify that you have sufficient access to that key, or contact your support personnel.
The problem here is that we have a mismatch of .NET. The simplest solution is to install latest version of a .NET and run the installer again.