Boot old laptop off of USB flash drive?

[Chris Jones <cjns1989@gmail.com>]

This old laptop's BIOS only lets me boot off of a floppy/CD-ROM/hard
drive.

Is there any way I could boot off of a USB flash drive - as in booting
off of a floppy or the hard drive and switching to /dev/sda when the
time comes to load the kernel?

Thanks!