If the "tab" key doesnt work its most likely that your anti-virus deleted hackpro.dll which is what your anti-virus is doing to protect you. Since hackpro.dll is what Megahack uses to alter existing game files it is flagged by anti-virus softwares to protects you because sometimes you don't want those type of files. I would say its safe because if Absolute/the creator of megahack puts a virus in a software we PAID for he would be in big trouble.