Re-start problems

Question

My iBook recently started performing extremely slowly, to the point where I lost patience and force restarted it. However it then only made it as far as the grey screen with the spinning wheel and apple logo. At this point nothing else happened apart from the wheel spinning endlessly.
I had everything backed up, so completely erased everything and started again, as recommended by an apple store employee.
This seemed to solve the problem, so I started updating, reloading programs and documents etc. and everything seemed fine. However as I was reloading my music, the iBook started making beeping and clicking sounds that seemed to be coming from inside it as the speakers were on mute. It then slowed to a crawl again and I restarted.
This time what looked like a page of command lines appeared, with just a black screen and white writing, the sort of thing you seen when you start windows. This seemed to be a repeating error message, which eventually gave way to the grey screen problem again.
Phew, sorry for the length of the post, does any one have any idea at all what is going on?
Many thanks

Answer 1

sorry i forgot to add on my last post that I have run both disk utility and disk warrior on it, both of which say that the hard drives is functioning normally. I also used the zero data option, which seemed to have worked until the problem resurfaced.
I don't entirely understand about the workings of a computer, but could it be something to do with the logic board and/or ram memory?