I have a Macbook and I got it November 2007.
Summer of 2010, I got a new hard drive (because it wouldn't turn on). Things have been okay since, but recently, it makes a weird noise and comes up with a warning in several languages, and says my computer must be restarted and hold down the power button. Today it did it 3 times altogether, including 2 times just now, in less than 30 minutes trying to watch Coronation St. online...

Kernel Panic.

Also if you're hearing noises it could be your hard drive failing again. I hope you're backing up.

hmm, I think it's because you were watching Coronation St.

Seriously though, if the hdd is making noises, it's likely close to failure.

- Have you checked the S.M.A.R.T. status or run Disk Utilities?
- What OS are you running?
- Have you had the kernel panic doing other tasks, or has it only been while watching videos?
- Are you streaming them or are they downloaded?

The noise is typically the full-out roaring of the fan, which is freed from any sense by the kernel panic.

The noise is typically the full-out roaring of the fan, which is freed from any sense by the kernel panic.

Further to MacFury's comment - it would help if you described the sound and when it appears. If it's a loud whirring that happens just as the kernel panic message appears, then it is probably the fans. This is normal fan behaviour in a kernel panic (the system, including the temperature monitoring that normally drives the fan operation has basically stopped working and the fans go into default full-on mode). If the noise is more like a clicking, clunking, scraping or otherwise not-so-good sound that happens well before the kernel panic message, then it could be the hard drive.

In addition to checking the S.M.A.R.T. Status of the drive, you should also look at (or post here, via copy and paste) the system log for the kernel panic, which you can find by following the directions here: Mac OS X: How to log a kernel panic (http://support.apple.com/kb/HT2546?viewlocale=en_US&locale=en_US). There may be clues in the logs, though sometimes they're difficult to ferret out.

The only time the noise happens is when that message appears. Other than that, it is working properly...

It's a fair bet that it's the fans you're hearing then. Please copy and paste the kernel panic log here, so that we can take a look and see if there is anything obvious. Repeated kernel panics are NOT normal and indicate something is wrong. The trick is figuring out what.

BTW - have you added any new hardware lately? (i.e.: new RAM perhaps?)