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.