External USB 2.0/FireWire hard drives, in capacities of 200 GB or more, are becoming quite popular. They're easier to set up and use than an internal drive, since they don't require spelunking around inside a computer. And if the inside of the computer is not readily accessible (i.e., a rack-mounted system), it's doubly useful. They're also extremely versatile: Many people are now doing full-system backups by simply plugging in an external hard drive and writing a backup image directly to the other drive.

Many of these drives come preformatted from the factory for quick use. This spares the user the trouble of having to go through the Disk Management console, mount the volume, format it and assign it a drive letter.

Unfortunately, many of these drives are preformatted as FAT32 volumes. This is quite deliberate, as there are still a few computers out there running earlier versions of Windows that cannot see or deal with NT file system partitions.

Sometimes this problem doesn't manifest itself immediately. For instance, if you connect the drive and use a backup product (such as Windows's own NTBACKUP) that writes the backup as one contiguous file, the backup may inexplicably fail after the backup program writes 4 GB. The reason is simple: The FAT32 file system cannot support single files larger than 4 GB. It can support large volume sizes, but no one file can be larger than 4 GB.

The solution is simple enough. The first time you connect such a drive, determine what file system it is through the drive's Properties page. If it's FAT32, reformat it as NTFS. The only exception to this would be if you're connecting to a non-NTFS-compatible system, of course.