can't u understand the trick?
any number between 1 to 10 multipied 9 gives a number with number index 9 so when we substrct 5 from it we got 4 and 4th letter of alphabat is D,that's why we all get the same results mostly :D :D :D
DOS password?i can't remember that we had passwords on DOS,we just copied command.com io.sys msdos.sys (or some other) and had fun,
i think u ar telling about BIOS password?
so do as xpert said or identify cmos clear jumper on m/b and clear it