HI Joachim,
Beginning with 9.0, VAST installations have been designed to be independent of one another, so you can install/uninstall any of those versions without
effecting other existing installations.
Though Environments will continue to operate, you should clean up (delete) any existing environments you have defined that are attached to the installation you are removing, and then remove the (9.2.1) installation from Environments as well. You can remove the installation using the "View/Edit Registered VA Smalltalk Installations" button (third button over at top of main Environments window). Note that Environments will not let you remove an installation that still has one or more environments attached to it.
Thanks,
Bob