There is nothing to fix, this is not really a false positive, it is a tool/program designed to kill applications/process, etc. depends on who/what installed or is using it (you/HP/malware, etc.), as it can be used for good or evil and avast can't determine intent, 'you' have to decide if it is Unwanted.
Even if you did move KillIt.exe to the chest, it won't destroy your PC as it is likely only to be used by HP if it is trying to do something like a restore, etc. It isn't a system file.