First of all the hardware requirements should be met: At least Pentium 166, 64 MB RAM, 500MB HD space
Sequence of Installation Steps: Install Oracle 8i first to its own directory (home) then install Dev 6 on a separate home. You may need to create a new home dir using windows explorer before starting the installation.
If you have made a mistake and installed some of the software but you need to uninstall use the CD_ROM to deinstall but this will leave something from the dir . So you use explorer to delete the whole Oracle directory then
use regedit to clean the registry (be sure to make a backup before you do this).