I just installed version 7 and I noticed that version 4,5 and 6 are still installed on my drive. Is it safe to remove them?
That depends on if you (still) have DAW projects that use these versions. Installing KONTAKT 7 will not automatically replace KONTAKT 6 content (exception to this is Cubase, Nuendo, MASCHINE and KOMPLETE KONTROL).
I would not remove at least 6, until you know 7 doesn’t give you any troubles