1-I had free avast on a windows pc and switched to linux-if I install on linux will the rootkit detection still be there?
Hallo, won’t be there - the rootkit detection engine is bound to windows version only (and is windows-oriented internally).
Thus, avast would still catch the rootkit’s visible parts (for example, when booting from live-cd, when the rootkit wouldn’t get control), but won’t be able to detect that it’s running inside rootkid-succesfully-harmed system.
But, there are some other free tools that can help in such situations: http://www.chkrootkit.org/
(honestly, it’s easy to modify any existing rootkit to be undetectable by this - anyway, when there’s a rootkit on the machine, the system was fully in the hands of an attacker, so you can expect everything).
regards,
pc