Go into you system, administration then software sources then UPDATES
and change release upgrade to normal or long term releases. then
reload and choose system, administration, update manager and check for
updates.
You'll have to upgrade to 8.10 before you should upgrade to 9.04.
OR the other way,
I did it successfully. I download 8.10 ISO alternative cd image, right
clicked it and mounted it and opened the link on the desktop and it
let me choose upgrade.
I then downloaded 9.04 alternative iso, did the same, and upgraded to
jaunty.
Please note that I had to take the gos theme off of the GOS cd and
place it on my system cause it (theme) got broke apart in the jaunty
9.04 upgrade.
BE warned, if you use a usb network device to get on the internet,
9.04 is a hoot to get them working. Stay at 8.10. I am going to go
back to it.