You can't uninstall windows 98 from within widows 98. You can try to delete everything and I don't know how far you will get but you'll never get it uninstalled properly. You'll probably just end up with an unbootable OS. You must uninstall while windows 98 is not running.
Before you do anything, make a full backup. This is especially important if you don't have a factory restore disk or the windows 98 first edition cd. Try using the free utility "Partition Saving" (
http://perso.club-internet.fr/guiboure/en/) to do this, or a commercial utility like norton ghost.
Now, you have several options:
Try creating a boot disk with windows 98 utilities (start-->settings-->control panel-->add/remove programs-->startup disk. Look at the floppy and see if there is an uninstall.exe program. If there is (I know there is on windows 95), reboot with the floppy and run it. I haven't used this method, so I don't know exactly what will happen. If it doesn't delete everything it might only delete windows98 leaving data intact. Be sure to be careful...
OR, you could just boot into dos with a floppy (like the one created above, and format the partition that has win98. This will delete everything, so be careful. To do this you would type
format C: (assuming that is your windows partition) at the A:\> prompt.
OR, you could go to the extreme and run fdisk and repartition the entire hard drive...
Note that there might still be remnants in the Master Boot Record, but this should not cause problems in you windows installation.
Be warned that if you have a really weird computer configuration this can cause very negative effects. So remember, I did warn you 
;D
Good luck,
~psi42
Linear Mode
