It looks XP has messed something with LILO (hope that only with it). To make sure your all Linux partitions are well boot from RedHat installation cd (in "rescue" mode), run
and press 'p' to list all partitions, 'q' to quit. See if all your EXT3 partiions are on place. Then try to mount your root Linux partion:
mount -t ext3 /dev/hda5 /mnt/linux
where /dev/hda5 should be changed to the righ partition in your system (fdisk results will tell you this).
When it's done use
to use your hd install as root dir and follow instructions from
(starting from part 5).