Sounds like you bought a 10.4 upgrade disk rather than a retail disk. Your machine came with 10.4 so will not boot from the 10.3.Your options are to click on my icon, contact me and ship me the hard drive for a free system install ( I need to know how much RAM you have so I know if I can take it to 10.5.8. Or contact Apple and buy an original system installation disk for $15 plus postage and tax. Return the disks you bought as they are worthless to you. IHS