Hi Visan,
My name is Igor, I have 12 Microsoft MVP awards. It's a pleasure for me to help others and I'll do all my best to help you. I'm sorry you have a problems.
To remove a password, please disconnect PC from power (wall outlet) and take out a CMOS battery from motherboard for several tens of minutes. This will reset BIOS and all BIOS settings.
Please check the PC has preinstalled Windows license because you cannot use school's license. Then you may reinstall Windows.