being nosey on sons laptop and set a password and now need to undo this but its in the boot system

If its XP see Password Recovery Software - Word, Excel, Windows and more...
If its unix/linux there are threads here, use the search function

By "boot system", do you mean Grub, or LILO, or BIOS, or MBR, or what?

I wanted to add links to screenshots here but I could not quickly locate any good ones. Grub has a frame around the menu and tends to have fairly long names for the operating systems. LILO is bare-bones, although there are many add-ons for adding framebuffer graphics to the boot menu. Maybe it's neither of these anyway.

If you have a rescue CD and can boot off that, it should not be too hard to mount the internal hard disk and change things on it. If the password is not on the hard disk, then obviously, this won't help at all; but for correcting LILO and Grub issues, it's a proven method.

By "boot system", I meant to say in the bios, these are the things I did to get my proplem,started the comp and pressed f12,enter setup,phoenixBIOS setup utility,arrowed to security,the user password is set and thats what I need to unset,and this is where everything is messy me up.

It's not particularly Unix-related then. Googling for "bios password" brings up lots of vaguely promising results.