There is no master password for every computer having windows installed. If that were the case the very purpose of passwords would be defeated. Anyone with the master password could gain entry to your computer and alter/damage the data which you want to keep safe and do not want others to be able to access.
There are programs available that allow you to hack in to a computer and access personal data without permission, but that is unethical.
In case you forget a personal password, it can be reset by gaining entry using the administator password or using a password reset disk. If you neither remember the administrator password nor have a password reset disk, you have to reinstall windows.