I've heard about this technique a few times and, having never tried it myself, I've always been cynical ... but by all accounts it looks like I'm wrong.
The basic idea is to put a failed hard drive in the freezer for at least an hour, preferably overnight, before trying to read the drive.
Responses to another blog piece on this include plenty of success stories, and a few clues about why it might work. The reason seems to be not the cooling per se but avoiding the heat generated in the drive when it is working normally. Presumably those delicate mechanical parts go out of tolerance when hot, or possibly the electronics inside the drive enclosure fail. Well that makes sense to me, anyway.
So, the techniques basically involve cooling and then keeping the drive cool enough while recovering data from it. You might install the drive in an external USB drive caddy and put the whole caddy in the freezer, or just use long IDE/SCSI/SATA and power cables. With long enough leads to reach a laptop or computer nearby, you would probably be able to recover the data from the drive without removing it from the freezer. Alternatively, you could try to keep it cool (perhaps even in situ) with icepacks (bags of frozen peas for example, or dry ice if you have some handy) but be wary of moving it directly to a warm room as that can create condensation (the critical bits are hermetically sealed, though, so in theory it shouldn't really matter). Either way, you need to work quickly, and be careful not to knock the drive - ordinary desktop drives are quite fragile. Don't install the cooled drive inside the computer, or boot from it, as both operations will just warm it up more quickly. Pre-boot the system from a good disk (a operating installation disk or recovery disk will do fine), get ready to restore the data to another drive, and then plug in the frozen drive, initiate the transfer and cross your fingers while the operation completes. It may take more than one attempt to recover all the data.
Having hopefully recovered most if not all of your data, it's time to develop a proper process for regular data backups. If you skip this final step, you really haven't learnt much from this episode have you? In fact, why wait for a drive failure? Sort out your backups now!
Gary Hinson NoticeBored.com