|If your computer is a laptop or netbook, you can enable a hard drive access password (must be known to use the hard drive) or a system access password (must be known to use the computer at all) in the computer's bios Setup.|
See the User's or Owner's manual for your brand name model.
However, if you forget the password, there is no easy way of removing it. Laptops and netbooks are very well protected regarding that.
If you have a desktop computer, you can enable a system access password (must be known to use the computer at all) in the computer's bios Setup.
See the User's or Owner's manual for your brand name model, or if you have a generic desktop computer, the manual for the mboard model.
However, it's easy for somone who knows what they're doing to remove it or them - by removing the Cmos battery on the mboard, or by moving a jumper on the mboard to the clear Cmos position, then moving it back.
You would be better off with a desktop computer using drive (data) encryption software that requires a password.
Someone who knows what they're doing can access your files via another user, or can delete your Windows users's password.
Or - anyone who knows how can install Windows from scratch, or the orginal brand name software installation from scratch, and use the computer
Whatever password you use, make sure it's something you will easily remember that is not really simple that no one else is likely to guess due to what they know about you or can easily find out about you.