guest account problem

what happened is i let my brother go online with my guest accoutn, but it seems he messed up the pc again , on control panel the guest account does not appear is gone, and when i try bootin up the pc the guest account appears with a password but cant seem to remove it, or just turn it off, help me guys and no he doesnt know the password, probabbly was exploited through one of windows flaws

Reply 1 : guest account problem

...then log in as an admin user and change the guest password or anything else you'd like. In Safe Mode, you should see your personal login account plus the hidden "administrator" account. If you've never placed a password on the hidden "administrator" account, simply leave the password blank and log in.

Hope this helps.

Grif