I'd like to keep my son off the computer when we're I'm not home. Other than taking it with me or any other extreme measures, is there a way I can set a password when the computer boots up so a login is required? I'm sure there is, but can't find out how to do it. I only want him on the computer when I want him on the computer.
Thanks.

You can set the password in the BIOS, that will prevent the computer from booting. Usually you have to press Del or F2 or another key while the computer is booting. If you see a heading for security it's probably in there.

There are ways to block the access of files or files on your computer. For Example, on This Question I replied with a link to a download of Advanced File Lock. This way you could block access to the files that control the internet, if that is specifically what you would like. You may also block access to the C:/ Drive essential files, temporarily.

I got it set up through the BIOS settings.
Thanks for the help.