My computer acting weird and start to going crazy?? What happen?

recently i donwload some kind of stuff on how to hack usenext to get account for free
i realised that it contain virus and i took risk to downlaod it because i think that my antivirus (bitdefender) can handle it
i also download some file after that
the problem is that when i scan the file (crack_keygen.rar) my bitdefender no problem and no virus detected. when i scan my hard disk, suddenly it scan that the file contain virus but it can be removed so i try to removed it manually and i succeed to do so
some file that i download also have virus and i removed them manually
then my comp start to going crazy it always hang and freeze
i become puzzle because i already scan using spyware doctor and bitdefender and there is no spyware or virus detected
someone plz help me to solve my problem

your PC is well and truly hosed
reformat your HD and reinstall windows
pray your motherboard and videocard bios wasn’t infected

Spyware Doctor v5 5 Keygen + Patch