As with the defragment utility built into Windows, Smart Defrag is a freebie that analyses your hard disk, shows you the results, and then lets you decide whether to defragment.
But Smart Defrag also offers extras as well, such as several levels of defragmentation, including whether to merely defragment your hard disk, or also move files around for optimum placement.
There's also a simple-to-use scheduler in Smart Defrag, so that you can schedule your defragments at regular intervals. You can also customise the defragmentation in many ways, such as not defragging when your PC is on battery power.
One particularly nice feature of Smart Defrag is Auto Defrag, which defragments your hard disk only when you computer is idle, so that you don't interrupt or slow down any work. You can also customise Auto Defrag by telling it to pause when your system exceeds a certain percentage of resource usage, for example.
Note that by default, Smart Defrag installs the Yahoo Toolbar, so if you don't want it installed, uncheck the box when you install the program.
A good freebie, we like Smart Defrag.