iBook problem!! Please help!

I bought an iBook of a guy on the internet with these specs: 1ghz 768 mb of ram, 40 gb hdd superdrive he put in blah blah blah. Well turns out there's some sort of problem with it that he didn't mention. When I first turned it on, the laptop started with fans blasting full and nothing on the display and nothing happens. So after a couple tries i got it to boot in to the welcome to mac os x intro screen, where it froze multiple times. Then, I finally got it to work all the way and use it and stuff but it freezes when the lid closes and won't go to or wake up from sleep when the lid closes. Now it won't turn on at all. Any ideas?

How do I boot from the cd drive? or a USB external hard drive

 

To my knowledge he's an apple certified tech and i checked under about this mac and sure enough it has a superdrive. I tried taking the extra ram out. No affect. I'm going to try and install OS X on to a external hard drive and see if i can get it to boot, but I need my cd out first

 

Well I can't even get it to boot to get my install cd out. All it does is turn the fans on full blast and then it just sits there. it sounds like the cd drive is doing something, but nothing ever happens. How do i eject the disc?