Fragmentation occurs when data is broken up into discontinuous pieces. Though Windows 7 automatically defrags its host drive, external drives and Windows XP still require regular defragging. Here are two excellent options.
IOBit's Smart Defrag surpasses the competition in two major areas: Smart Defrag is faster, and it utilizes a perpetual defragger that runs as a background process but doesn't slow down your system.
When running in the background, the program only eats up 14MB of RAM, so it's possible to run it smoothly even on older machines. Along with quick analysis and scans, Smart Defrag boasts a scheduler and some customization features, like offering a deep defrag versus a less time-consuming one, and running at boot-up or shutdown. Overall, it's a handy defragger with plenty of options for both novices and power users. Read full review
Auslogics Disk Defrag is another excellent choice, with only slightly fewer options than Smart Defrag. An easy-to-read drop-down menu holds your hard-drive selections; choose one and Disk Defrag instantly displays the drive's size, used space, and free space. The program even displays a pie graph for you visual types. The sector map makes it easy to see how much of the drive is fragmented, allocated, and free. As the program churns away, the defragged sectors are displayed in blue. There's also a real-time defragger that can be set to run while your system is idle.
Disk Defrag is fast, even on older XP systems. A handy HTML report is prepared after each defrag session. The summary displays total files and folders defragged, and the detail section lists the defrag outcome for each file. A final sector map is lacking, but novices and system administrators alike will get a lot of mileage out of this defragger. Read full review