Use the free software product Smart Boot Manager. The Linux kernel no longer fits on a single floppy. SBM makes one floopy that can boot any bootable CD on a computer where the BIOS doesn't support boot of CD dricves directly. You can also elect to install it to the hard drive MBR if you wish, and that way you don't need to use a floppy at all and you can still boot from the HD or the CD.. Search for it with Google, it's an easy find.

You might also want to look at XOSL. I think it's much nicer and more powerful, but it does have to be installed to hard disk, you can not make a boot floppy with it.