When you first boot, you get the "Press F2 for Setup" (or something like that), Does it also give you "Press F12 for Boot Options" or "Alternate Boot press F??" or some such ? . . sorry for being cryptic, but I don't know your system.
If not, you gotta get that BIOS password or you will be unable to boot the Live disk! and will be left with mint4win as your only choice, running Mint from within Windows. (I've never used mint4win, but just go to the mint4win section of this forum for info, or the Mint Wiki)