I just looked at
the DetectX home page and found "
For MacKeeper, it is important to follow the instructions on Applehelpwriter(*) for how to uninstall MacKeeper properly."
I posted that a while back; have you tried it?
(*)
how to uninstall MacKeeper – updated | (The instructions specifically mention the file you originally referenced, i.e. /Library/Preferences/.3FAD0F65-FC6E-4889-B975-B96CBF807B78)