verze 1)
skoc do BIOSu - Advanced BIOS features - Security Option - zmen to na "SYSTEM" a zahesluj BIOS, pak by to nemelo pustit bootovani dokud nezadas heslo do BIOSu

verze 2)
skoc do BIOSu - POWER Management Setup - Power On Function - zadej "Password", objevi se policko "KB Power ON password" a tam zadej heslo. Pak se bude komp spostet ne tlacitkem na bedne, ale zadanim hesla na klavesnici

pokud tvoje sestra nevi, jak se dela "clear CMOS" na fosne, tak by to melo pomoct.