Couple things: is your / partition on a primary partition, and flagged bootable?
(use cfdisk or a Windows partition utility to check)
What did you do with the 8.4GB HD? Reformat? Or does it still have OS's installed on it?
Check your BIOS boot order - usually by hitting F1 at startup - to make sure it's checking first floppy, then CDROM, then hda, then hdb. (or whatever you'd like, but if you're booting from a floppy make sure it checks for floppy before HD)