Missing space on my computer

So without me downloading or adding anything to my computer I hav
Slowly watched the gigabites disappearing from my computer. Now this ha
happened over a period of time so I've been taking corrective measure
and trying to reallocate items onto disks etc. but in all truth its
bit beyond me whats taking up all the space

It says that I have 450 GB on drive C. Total. I've been looking at th
files and the folders on the drive and I can only account for around 25
GB of space being used combined between music movies and programs.
don't think I have any hidden files... and literally I watched 5 g
disappear in the corse of two weeks and I can't figure out Why

I have started using a disk defragmenter to try to free up space.
decided to compress files in a couple of the files and I have gotten 3g
back within the first hour of doing this but it still seems strange t
me and I was wondering if something else might be the matte

--
Sinesthera