If, while troubleshooting your PC, a tech-support person says you need to defrag your hard drive, you have my permission to laugh directly in his or her face. In the history of computing, defragmenting a hard drive (the process of relocating file fragments into a contiguous area of the drive) has never, ever solved any real-world problem with any PC.
Of course, that doesn't mean you shouldn't do it once in a while. And although Windows has its own defrag tool built in, there are better options. One of them is IObit's new Smart Defrag 2, which promises "the world's fastest defragmenting speed" and real-time, background operation.
I can't say for sure if Smart Defrag 2 is the fastest utility of its kind, but I did find it easy to use. After clicking analyze, I waited for only a minute or so while the program scanned my system and issued a recommendation ("Defrag and Fast Optimize"). That option took about 90 minutes to complete.
The program features a "boot-time" feature that can defragment system files during the boot-process--files that wouldn't otherwise be accessible (because they're not safe to move while Windows is running).
Smart Defrag 2 is free, so you have nothing to lose by giving it a try. That said, you may also want to check out Piriform's Defraggler 2.0, another freebie. The key takeaway here: defragmenting your hard drive every now and then is a smart move, and you don't have to spend any money on software to do it.