Computer Tech Help Please! I want to learn as much as I can about my new pc running windows 7?

I really want to be able to understand my pc and windows 7 inside out. I want to be able to look at files and folders and know what they are and whether its safe to delete them, as opposed to constantly not knowing what some stuff on my computer is or does. If anyone knows any worthwhile text to read (book or webpage) or any videos that would help, PLEASE let me know!