If your hard drive dies, freeze it and it will buy you enough time to retrieve its data.

As the myth goes, if your drive dies (for whatever reason) and you cannot access its contents, just chuck it into the freezer for a couple of hours. Once it's nice and cold, quickly hook it up to the PC and it will run for some time, which should allow you to to retrieve some, if not all, of the data in the hard drive. The key, apparently, is to do it while the hard drive is cold.

As encouraging as it may sound, this is is just a myth. Most hard disk drives can work at freezing temperatures, as low as 0 °C. However, if the hard drive is already dead (e.g. because of a head crash or damaged electronics), you cannot revive it even temporarily by freezing it. Unlike ice-cream, hard drives really do not need to be frozen.

Incidentally, modern hard drives now use fluid bearings which cannot work below a certain temperature. Freezing the hard drive below that temperature will actually prevent the drive from running, much less restore its operation.

Hard disk drives run better / last longer below ambient temperatures.

This is quite a rare myth, possibly connected to the "frozen hard drive" myth above. Both are based on the premise that hard drives work better when they are really, really cold. The colder, the better.

Hard drives can operate at a wide range of ambient temperatures, very often from 0 °C to 60 °C. This is far in excess of the normal room temperature. This does not mean they work best at either extreme ends of their range. The Google report aside, hard drives can be damaged by high temperatures. So it pays to keep them cool.

However, freezing them below room temperature using a peltier (thermoelectric cooler) is not advisable as water can condense on the drive or cooler, and we all know that water and electronics do not mix too well. So you had better think twice before you hook up a peltier to your hard disk drive bay!

You will lose 64KB of capacity everytime you format the hard disk drive.

Another urban legend used to scare those who are thinking of formatting their hard disk drive. Who likes losing storage space, even if it's just 64KB?

Well, you need not worry. You will NOT lose any storage space everytime you format the hard disk drive.

Note that some of the hard disk drive's capacity will be reserved for use by the file system. The storage capacity isn't lost. It's just used by the file system.

If you format the hard drive more than xxxx times, the hard disk platters lose their magnetic properties due to repeated reorientation.

Repeated reorientation of the magnetic field on the platters actually reinforces it. Everytime the drive heads writes new data to the platters, the reorientation of the magnetic fields refreshes their strength.