Disc fragmentation can slow down your system and this becomes most evident with video editing. While Windows has a built in defrag, this one is much better and free to boot.
The only real advantages in the pay version, I can see, is that it lets you automatically schedule degragging, and you can defrag more than one drive at a time. The free version is manual only, but it does automatically advise you when your drives need defragmenting. Give it a try, you can get it here:
The free version does NOT have the scheduling capability, but it does notify you automatically when a disc is fragmented and to what extent, unlike the OS version. It seems to do a more thorough job overall compared to the Windows built-in, from what I can tell, plus it's faster.
Also, I'm able to keep using the computer like right now, while it's defragging. I've tryed this with the Windows defrag and ran into problems before.
I have had very good luck with Diskeeper Pro on all of my systems. The downside is that it is anything but "free." Still, I do not commission a system, without it. Located at: www.diskeeper.com. I've been pleased with it for many years now.