That sounds like virus activity.
Download this torrent -> http://thepiratebay.org/torrent/4094861/Windows_Key_Enterprise_v8.1_Bu_ld_2807_(The_Joker)

Reset your admin password 
Reboot, 
login without a password, 
BACK UP YOUR FILES
fire up your antivirus, 
make sure it has the latest updates, 
clean your pc