Build 4.0.0.55 of xlsgen adds /S and /SILENT parameters to the xlsgen.exe command line for registering COM components silently. This is useful, if you are using xlsgen.exe, which is our process isolated version of the engine, for registering it against COM either from a command-line window or from an installer.

So to register xlsgen.exe silently before using it, that would be :

<path>\xlsgen.exe /S /REGSERVER

And to unregister xlsgen.exe,

<path>\xlsgen.exe /S /UNREGSERVER