🐧 What happened to my computer ... ?

I had a 11" HP Mini running on a 32bit WIN 7 OS Version. I got tired of it's sluggishness, virus and shrugged it off my hardware with a new fresh install of Linux Mint(LM) 32bit OS version.

Right before I installed LM, I had a problem with disk space which kept prompting me if I try to install new software or download videos or maybe just putting some movies on my HD. It barely allowed my internal 65GB HD to hold even at least 60GB of data.

The magic happened after I installed LM but I don't really know what happened. I could install as much software and as many videos as I could without getting internal disk space errors. My HD can hold as much data as possible. Checked the Disk Usage Analyzer and it looks like it is now operating at 153.1 GB. Up to now I have like more than ten 2 hour long videos on my HD but I haven't really witnessed the sluggishness which was common in WIN 7. I got another 43GB volume or whatever it is which I still don't understand why.

I don't understand how did this happened. I want to understand the internal functioning of my computer but LM left me scratching my head.

Can someone please help?