A hard drive partitioning program primarily written for windows, but with a dos version that can be put on a boot disk and used with any operating system. It can non-destructively resize FAT(X), FAT32(X), NTFS and EXT2 filesystems, it can clone partitions, copy them from one drive to another, and change the cluster sizes of fat and NTFS. Newer versions (5+) can merge fat partitions together, and perform operations on unused partitions while windows is running, and without rebooting.
Partition Magic is, however, slow. It ignores obvious optimizations, creating hours of extra work for itself: If it is fed a long batch of resize operations it makes no attempt to reorder them, and can end up doing stupid things like shrinking clusters only to have to grow them back again. The most noticable inefficiency is its inability to grow a partition towards the start of the drive: instead it moves the partition up the drive, and then grows it towards the end. When moving a partition to a new location that overlaps the old location, instead of keeping the data in place and adjusting the metadata, instead it robotically moves every single sector. These two inefficiencies have the consequence that adding a few megabytes to a the front of a partition can take hours, while doing the same to the end takes seconds. A behaviour of Partition Magic which may cause concern is that it is often lax in updating the screen, giving the appearance that the machine has crashed. In some cases, even the Caps Lock light will not work. However if it is left for a few hours uninterrupted, Partition Magic will complete its run.
Partition Magic has an inexcusable flaw: it writes to partitions and drives when it has not been told to, and even when it has been told not to. It uses the MBR of each drive to store its per-drive settings, which means that checking the 'set drive as read-only to Partition Magic' box will actually write to the drive!. If there's a program in the MBR that it doesn't understand, it will just write over it anyway. Don't use Partition Magic when a drive that has Smart Boot Manager is attached, or it will write over SBM and render the machine unbootable. It will also write to bootsectors of partitions it's not working on, and will try to edit NTLDR's boot.ini (even when it is on another drive than the one you're working on) often leaving syntax errors that break the bootloader.
Partition Magic is a very attractive trap: because it promises to resize partitions non-destructively, it naturally gets used on partitions that are not backed up, and contain important data. It then usually works, but if it crashes, encounters a bad sector, or becomes confused, it buggers them up royally. Partition Magic recommends working only on drives you have a backup of, but I'd go one further, and recommend disconnecting any drive you're not working on, only using the dos version, and booting it from its own dedicated hard disk. Backups should be done with dd or ghost, so that when it breaks the drive, the whole thing can be restored, MBR, bootsectors and all. In fact, I'd recommend not using Partition Magic at all.
The retail version of Partition Magic is licensed per machine, and is non-transferable. Once it is used on one machine by one person, it may not be used on any other machine, or by any other person, even if it is removed from the first machine. Interestingly, the license doesn't go into much detail as to what constitutes a computer, so what happens when every component of the computer is upgraded is left undefined.
Many countries have ruled that the First Sale Doctrine applies to software, preventing copyright holders from controlling the resale, lending, and giving away of their products; such legislation would probably mean that Partition Magic's license contains a number of unfair contract terms, rendering it toothless. This should not be taken as Legal Advice - I urge you to familiarise yourself with consumer protection laws that apply to you, and to consult with your lawyer before breaching any contract.
Partition Magic is produced by PowerQuest, who have a website at http://www.powerquest.com . Enquiries about Partition Magic can be emailed to firstname.lastname@example.org