Imac A1224

I know I know, IMAC, but I thought I would ask. I have two of these that were given to me and I would like to restore them and sell them and need some info on how to go about this. So far I have tried the command key and all it gives me is the hard drive and I select it and it boot to the desktop. Is it I will have to buy the cd's for this or is there a simpler way.

There is a LOT of info here -> http://www.mac-forums.com/os-x-opera...-computer.html

Wow a windows pc you pop in a disc and install the system. Mac you have to research for a month to figure it out. Glad I use PC.