Itunes 10.6.3 for OS X Leopard 10.5.8 on Powerbook G4 reinstall not working??

Hi guys, I am trying to get my old powerbook G4 ready for sale and I put the Leopard disk in and chose the "erase and install" option. Everything is good but itunes is saying it needs quicktime to be updated to a newer version. I found a thread with a link to the itunes download of 10.6.3 and everything downloaded fine but I go to open itunes and it gives the same message?

Am I missing something here?