It's in one of the first menus of the BIOS setup, usually like <B>Floppy Drive A: 1.44 MB 3.5"</B>. Basically make sure you don't have it set for B: instead of A:, and in another menu there should be ...
it's actually CMOS that you have to clear, if you're sure you're using the correct jumper, try removing the CMOS battery for about 5 mins.