Computer Boot Problems!! Help!!!


I got this iMac from a friend. This is the first time that am using an apple computer. As I switch it on, the computer starts and goes into a grey-ish screen with an animated icon in the middle that looks like a folder with a question mark and the OSx logo.... and stops there and I cant get past that.

Any ideas as to what I have to do? Is the computer busted?

Please help. Thnx
Unknown information:
iMac model.

'Is the computer busted?', - I doubt it ... since you do have a grey screen with a question marked folder displayed.

'Any ideas as to what I have to do?', - Well, you could ask your friend if he erased and / or re-formatted the iMac's hard disk drive, hdd. If he did erase and / or re-formatted the hdd, did he then re-install a new System / MacOS on the iMac?

Did you receive any Installation and / or Restore CD(s) with the iMac?
If not, you need them; or, to purchase a System / MacOS X Installation CD disc set (or DVD disc, if applicable) supported by your (unknown) model iMac.
Well this is the thing... my friend got this from her husband who is in Hong Kong. Her husband bought a new one so he pushed this over to her. She was using this for awhile, then she came to me saying that all of a sudden it doesnt work. She might have done something to the mac software but she doesnt know what... she aint a computer wiz.

She didnt get any cd(s) with the iMac either.

So my only option is to re-install mac osx, is it?
I want to know... what are the common executable file extensions for a mac?
The icon you're seeing clearly says: "System not found." Install the system, then. Nothing's busted, the computer just isn't, well, installed.