dos help

I’ve accidently installed part of dos version 6 on my computer. the boot disk w/ this version doesn’t contain fdisk or anything. i need to get off dos 6 and install win 98 se but it won’t read the win 98se boot disk. if i try to run fdisk from the win98 disk it says incorrect version of dos. so how do i get rid of version 6 and install win 98 se. Thanks in advance for your help.