Please Nairalanders, help me out - my MacBook (2.4 GHz, 250GB HDD, 2GB RAM, 2008) ain't working.

I was using iMovie to edit/join some videos during which I got error messages. Eventually the edits could not be completed. Then the Safari web browser began to slow down with the annoying SBBOD. The startup time got longer and the system got slower. Indexing (from Spotlight) became noticeable and started to last for about 45 mins after booting. Then I used Onyx to carry out checks and repairs, and the system speed increased a bit. I switched it on one evening only to see a grey coloured screen with this symbol -


I tried to use the install disk for repairs but the only option available was to re-install which I started only to find out that it would take about 18 hours. This I had to abort upon considering the Lagos power cuts but there was a warning on the screen about stopping the process - the computer may not startup.

The next time I tried to power on the MacBook - 2-3 weeks before the transition of Steve Jobs - there was no response; nothing to indicate that anything is working apart from the battery indicator. The install disk is also stuck in the optical drive.

Could there be a problem with the hard disk as the MacBook has fallen more than once?
Could there be a problem with the motherboard?

You may want to post you issue here in this thread: Post Your Imac, Macbook And Macbook Pro Problems Here.
It's a thread dedicated for macs

I have modified my entry on that thread by including (copy + paste) the issue at hand.