If you were installing 98SE from a bootable CD and it asked for a format it was because you probably had your XP on a NTFS partition which 98 doesn\'t recognize, so I think you lost all your data (there are some utilities that will let you recover your data though, but NTFS....dunno...)
If you can\'t boot from a bootable CD or from a floppy that\'s a big problem (make SURE the right boot order is set in BIOS). Anway, when trying to boot from a CD, even it\'s bootable or not you should see at least a message like this: Booting from ATAPI cd-rom... or if you try to boot from floppy you should see its led lighting up when trying to read the disc in order to boot from it.
As you describe the problem (first the format ends up unexpectedly, then it doesn\'t boot from any bootable CD or floppy) I would say it\'s a hardware problem. In such cases try isolating the hardware that is causing trouble: remove any additional hardware from the computer (add-on cards - sound card, network card, cd-rom, mouse, anything). Just keep your video card, RAM and floppy. Even whithout the hard-disk it should boot from the floppy if everything it\'s ok. If it boots, shutdown, plug-in one of your hard-disks, boot again from the floppy and see if you can see your disk using fdisk.
This is just to have some secure starting point - try it and keep us up to date with how eveything goes.