Well, you should have at least OS X 10.2 installed on it to be able to do most things you are familiar with. As for running Windows, you can't install it directly, only by emulation, and it's so slow that it'll be like a 486. Once you are running 10.2 you can then use either Safari or Firefox and then goto Adobe's site and install Flash and you can youtube to your heart's content. As for getting your hands on 10.2, ebay will be the best place, just make sure that it is a retail copy of the installer. And then also make sure that you have at least 256mb RAM installed too. To find out the hardware and software stats of the iMac, click on the Apple in the upper left corner and goto "About this Mac" or System Profiler.