Activate admin account through command prompt

If you own the PC make him give you the password.... Its a very simple solutions.... why would you have given him an admin account on YOUR PC if he cannot be trusted.

Toms hardware does not allow disscusions about bypassing security or passwords. Please read the forum rules. if you truely cannot get him to give you the password you will need to contact the manufacturer and provider proof of ownership. As your OEM they are responsible for windows support.

i did not log off before leaving my computer, my brother is also currently on holiday, and he used my account to create himself an admin.

Thats all well and good but it does not change the forum rules, or the fact that we have no idea if you own the computer. If your brother would do something like that don't let him in your house, and lock your computer. If hes "on holiday" call him. If you can't call the manufacturer