im having problems with adobe flash player installing on my apple powerbook g4

i have downloaded adobe flash player several times cant seem to get it to install. i dont know much about this computer honestly i just got it and had to do a factory reset on it in order for me to get into the computer itself and that took forever and so has this. i need help badly.

i tried to open adobe reader 9 and got this error message:     There was an error opening this document. There was a Macintosh system error (-1409).

i dont know what this means what to do where to go who to talk to about how to solve my problem.