When burning CD you not must burn the iso file.
It´s a different option of normal burn!
When you open your CD , you must see SEVERAL files and not just a .iso file!
BEFORE THIS
Just be sure your CD is OK and can boot on other computer!
After be sure...try to do "FDISK /MBR"
after boot from Win98 disk/CD
So he never will boot with old OS!