To have to purchase a retail disc and not one of the OS X install discs that come with new machines. Retail discs are black. From the sounds of it, you tried to use a grey disc (machine specific disc) which, as you found out, will not work on your machine.
Even if you do get Tiger installed, you still don't meet the system requirements which list a "PowerPC® G3 500MHz or faster processor" as a minimum. Even if you could get it to work on your machine, the performance would be horrible.