umm which hack... there are multiple... and u said that u injected it?
ill just start from the beggining.
get the hack (depending on which one turn off antivirus)
open the .rar
put .dll onto ur desktop
get an injector
run injector as admin (if ur using win xp skip this)
browse for .dll (if needed)
press inject
start combat arms
when ingame press the insert button (unless specified otherwise)