Thanks For Ur Question and choosing seven forums ,
There are n Number of ways to Break the Windows 7 Passwords, guess i have 7 more tips pretty handy works all the time
Yo Brother might have turned on the Guest account when u allowed him to work with ur laptop with admin privilges, so he might have enabled Guest account , Then Instead of typin Your User name in the logon screen , he would type GUEST that allow him to Log on into ur Lappy
: This is the awesome Trick all the Windows 7 and Vista Have Hidden Administrator Account , I reckon he might have enabled that and trippin you Bro,
To Enable that Fire Up Ur CMD Prompt with admin elevated Mode
Built-in Administrator Account - Enable or Disable
He might have done this also , Looged in ur Lap using the Guest account and then he might have typed CONTROL USERPASSWORDS2 In the Run Commannd ...from that He might have added a new account for Him !
: With the Guest account he don have admin Privilges to his Command Prompt, But There is a exploit for that , Click on start Type CMD in the search Box, then Press ctrl and Enter that will pull a CMD Box from windows/system32 folder with elevated admin mode , then he may begin launching the User add command to add a account for him
(There is still two more method and also One is that you need to find the cmd.exe in windows folder rename it to sethc.exe then Log off the system and press Shift key 5 times it will bring the CMD in elevated mode And another method is Open up the Notepad Type @echo off command.com and save it as cmd.bat ...then log off and click on that it will bring the cmd in admin mode )
c:\windows\system32\ user add Corrupt DNA (This will create a new user profile for him)
Number 5: Ophcrack Live Or Hirens Boot CD , Or NT Offfline Password Recovery Or KAIN and ABEL software may be Behind this Brotherlyhood Playin games !!
Number 6 : KONBOOT also may be the Behind the scenes