Afaik, there is no registry trick for adding such an option in context menu.
Coz none of windows DLL files contains such method to close the tray.
But there is a workaround to get the "Close Tray" option in context menu of CD drive!
Just install
Virtual Clone Drive from
here. Its just 1.05 MB setup file. After installation u'll get an option to close tray in the context menu
Actually this software installs a DLL file
ElbyVCDShell.dll, which contains a method to close the tray.