The error you specified means the hard drive was not bootable at that time. The klunking is probably the R/W heads recalibrating, which means they got lost, (or a might bewildered, as Davy Crockett put it) which ain’t good.
I would probably look on ebay for a replacement (buy from somebody with lots of very good feedback). Or try one of those big chain stores. Circuit City etc.
You could try resetting the BIOS to defaults and unplug a reconnect the hard drive. It could also could be low battery related but not likely. You backed up your writing and that’s good, but my computer tends to accumulate stuff that I don’t remember until I need it. Yours may be similar. So backing up the entire drive is a good thing to do. Once you do that you can continue to use the computer until it fails. You can probably connect it to a desktop computer and just back up everything to its hard drive. There are lots of ways to do that for not much money.
Hope that helps. Good Luck 🙂