windows defender

when trying to remove windows defender from add remove progs i first get the
message windows installer could not be accessed this may be because you are
in safe mode or it is not configured properly. When i click ok it says
preparing to remove then says fatal error during instilation! i have two
volumes on my computer after repair one that works fine and the other not.
could this other volume be conflicting and if so as it is no longer usable
can it be safely deleted? please help
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