5.0 boot.img floppy doesn't boot

[Dave Barr <barr cis ohio-state edu>]

I've got an HP Vectra, PentiumPro 200, with a 3com "Vortex" ethernet,
and Adaptec AHA-2940A SCSI host adapter, w/ a SCSI CD-ROM.  No IDE devices.

This system has been running NT 4.0 and RedHat 4.2 flawlessly (booting
with LILO).  I had recently upgraded the kernel to 2.1.71 and that worked
fine too.

I decided to try out RedHat 5.0.  I downloaded boot.img and supp.img
to floppies (dd if=boot.img bs=1440k of=/dev/fd0) and tried to do
an install.

The kernel appears to load, and after uncompressing the kernel it gets to
"Now booting the kernel" and then the system resets and reboots.  None
of the usual kernel startup messages appear.

That's as far as it gets -- I've tried "expert" mode to and it does
the same thing.

I had purchased 4.2 so I had installed off the bootable CD last time.
I tried booting off the 4.2 installation floppy and that worked fine, so
this appears to be 5.0-specific.

Any ideas?

--Dave