I've got a couple of installers, all of which I've been told are universal and not machine-specific.
The installer will only work if it is on the original CD or if it is made to believe (forgive the anthropomorphism) that it is on the original CD. If you do not have the CD itself, the installer must be on a disk image that is an exact copy of the original CD, usually a .iso image, and the file must be locked to appear to the installer as a (read-only) CD. (Booting from a writeable disk image will change its content, so it may not be useable as installer disk after that.)
If you have an .iso image file of an original install CD, you can also burn that .iso to a CD. That CD should then be an exact copy of the original CD and can be used as such. Note that burning a .iso file to
a CD is not the same as burning a .iso file onto
a CD. See: http://www.petri.co.il/how_to_write_iso_files_to_cd.htm
For upgrading from 8.6 to 9.0.4, you will need a full 9.0.4 installer or a full 9.0 installer and a 9.0 to 9.0.4 updater.
(The new world rom from the Redundant Robot site should be fine for both 8.6 and 9.0.4.)