iBook crashed and don't understand why

OK I'm new to this and haven't found anything like my problem on this website but about a month or two ago our iBook G4, which I am on right now, started to make a weird sound every so often. At first we just ignored it but then in the middle of backing up our HD the laptop started to make that sound again.
I was backing it up in one account while working in iMovie in the other and it froze. I shut it down by taking the battery out because it would not turn off any other way. I put it back in and it got to the loading screen and started to make that noise again and froze up. We recovered everything on that hard-drive and got a new one put in but I was hopping one of you fine people could tell me what went wrong.

Thanks in advance

I understand that but what might have caused that to happen because none of the data was saved to the backup disk and it was just about done

windowpain said:

and lucky it wasn't you swapping out the old drive!

Click to expand...

ya i guess i should feel happy and ya all but a locked file was recovered i don't understand why becausethe people were able to recover everything except one user file that was locked, anyone know why?