How to free up space on my pc?

I have 186gb worth of space on my laptop right now, I just installed windows 7 and a few other programs to help get myself going again, nothing that would take up alot of space. I did a disc cleanup and Im in the process of defragmenting. But I dont understand. When I had windows xp I had a ton of programs, plus wow, plus another videogame, plus a ton of anime files and music files all backedup in folders on my laptop. And it still had about 15% space left or higher. why is it so different now? thank you