My wife carries a portable 40 GB 2.5" drive back and forth to work, and has on it all her professional and personal files (30 GB); in other words her digital life. It has worked fine for the past 4 years, and she treats it carefully. However, without warning and without reason, it simply would not mount yesterday. I tried everything; I could hear the drive spinning and feel it running, but it would not mount so no utility could touch it. It was obviously some kind of mechanical problem. I removed it and installed it into another working case, but that didn't help. I guessed it was the end of her data on that drive, and the only backup was months old.

And the solution? Putting the drive in the freezer!

I enclosed the naked drive in a plastic bag to keep out moisture and froze it overnight. Then in the morning I let it warm up for several hours and plugged it in. I let it run for about an hour to get it warm again (like drives normally get when running; remember the drive would spin but not mount). And it mounted, and ran fine! And I was able to copy all 30 GB of data to a new drive. The theory being that the freezing caused parts to contract and the rewarming caused them to re-expand and this release the stuck parts (probably the read/write arms).

[kirkmc adds: This hint follows another hint about cooling an iPod to get it to work that was published a few days ago. Several people mentioned similar techniques in the comments to the previous hint: either putting a drive in the freezer, refrigerator, or simply on a cool-pack. While this sounds like hard-drive voodoo, I'd certainly try anything if I was in that situation.]

This hint is not specific to OS X, but I think it's worth sharing as it might save you a lot of time and heartache!

If you have a dying hard disk (it might have started making clunking noises, or is reported by Disk Utility as 'failing'), try removing it from your Mac and placing it in an external HD enclosure if you can. You will then be able to change to orientation of the drive (stand it on it's end, or lay it upside-down). If you're lucky, a different position will allow the drive platter to spin smoothly for long enough to get your data off.

It worked for me! In the space of the last hour I've gone from deep depression to skip-round-the-room-singing joy as I've just recovered all of my data from my PowerBook's dying HD.

I was looking at my desktop and noticed that some of the drives show the total space and free space, but some only show the total space, as seen in the image at right. It took me a few moments to figure out why this was happening: the drives which only show the total size are formatted in NTFS, and therefore are mounted read-only.

Any read-only drives will only show the total space, and not free space. This seems a little strange, since I might want to know how much available space I have, even on a hard drive mounted read-only. With some read-only media such as CD-ROMs, it wouldn't make sense to show "available space," but for hard drives, I wish it was available.

Tip within a tip: Unix geeks can go into Terminal.app and run /bin/df -h, which will show total size, space used, and space available for even a read-only disk.

This may be already known, but it was a surprise to me when I created a slideshow with iPhoto and iDVD. Although the Pioneer 111D DVD writer is shown in System Profiler as being unsupported, I was offered a choice of the internal UJ-846 or the Pioneer to burn my project to. I next tried burning a folder, and it also burnt fine, as did iTunes.

This is on an iMac G5 with Tiger 10.4.7 and the drive in a FireWire case. It makes me very happy, after many fights with the UJ-846 to try and get it to burn a DVD reliably -- I have enough coasters for a very large party :-). I have seen reports of the Pioneer 110D working fine, but none for the 111D. Anyone else care to report their experiences if they have one of these drives?

To make an external bootable hard drive with both HFS+ and NTFS file systems, do the following.

First use Disk utility to partition the drive. Make the first partition HFS+ and the second partition as MS-DOS (FAT32), making sure you go into 'Options...' and check the GUID radio button (to make the HFS+ partition bootable on Intel). Then follow these steps to complete the process:

1. Connect the hard drive to a Windows machine, and wait for the FAT32 partition to mount.
2. Open My Computer and right-click the FAT32 partition and select Format.
3. Format the partition with an NTFS filesystem.
4. Remove the drive from the Windows machine, connect it to an Intel Mac, and install a disk image built for Intel Macs. (You can try a Mac OS Install Disk, but this is how I did it.)

[robg adds: I haven't tested this one.]

Hard drive space is still a premium on laptops, and media files can eat a lot of that space. Here's a little trick to minimize the space taken up by applications that are not used frequently. It's a simple idea -- put the individual applications on individual compressed disk images using Disk Utility. Then create a folder for the disk image, and put an alias (pointing to the application on the image) in the folder with it. Store this folder in your Applications folder.

Some people may prefer to put all of their less frequently used applications on one compressed disk image. I prefer keeping just one application per disk image, since it takes less time to verify and mount the image. The compressed disk images take up far less space than the full application. In many cases, the disk image is at least 60% smaller than the full application.

When you need the application, just open the alias. The disk image is automatically mounted, and the application opens. It takes a little longer to launch the application, but it should be entirely acceptable for applications that are not used daily. Using this technique can free up a significant amount of drive space.

[robg adds: The only caveat with this method is that you may have issues during software updates -- the software updater will expect to find the applications in their standard location, in an uncompressed form. To be safe, you'd want to expand and copy all your compressed apps back to their normal locations prior to running a software update. But that could be problematic if you've used up all the space freed through the compression trick -- there won't be enough room on the drive for the expanded apps. I would recommend using this trick sparingly, and then only on the largest of rarely-used apps (GarageBand?), where you'll see the greatest space savings -- and remember to undo what you've done prior to running an upgrade. For third party apps, however, this seems like a very good solution (though you'd probably have to delete and recreate the image each time there was an update).]