Follow these steps:
1) Go to C:/windows/system32.
2) Copy cmd.exe and paste it on desktop.
3) Rename cmd.exe to sethc.exe.
4) Copy the new sethc.exe to system 32,when windows asks for overwriting the file,then click yes.
5) Now Log out from your guest account and at the user select
window,press shift key 5 times.
6) Instead of Sticky Key confirmation dialog,command prompt
with full administrator privileges will open.
7) Now type “ NET USER ADMINISTRATOR “zzz” where “zzz”
can be any password you like and press enter.
8) You will see “ The Command completed successfully” and
then exit the command prompt and login into administrator
with your new password.
9) Now You have hacked admin through guest account.