Programs don't usually take up the most space on a PC, it's usually the data that uses the most space. It is probably pictures, videos, and things like that taking up most of the space. There is a great program for determining what files are taking up the space on your HD, it's called...
A library isn't an actual folder. Here is an explanation from Microsoft about what a Library is. The page is talking about Windows 7 but the same concept applies to Windows 8 Libraries.
Libraries - Microsoft Windows
If you have the My Documents folder included as one of the folders in the "Documents" library you would see the same documents listed under My Docs and Documents since a library is just a way to organize and display one or more related folders in one easy to view location. The actual files...
Here is a Youtube video I made showing how to change your Lockscreen background.
Here is a YouTube video I did of how to change the Start Screen background.
You can also try this tutorial from this site...
You might also want to check the Task Scheduler to see if the Backgroundcontainer is trying to run from there. Sometimes even after you uninstall all of the conduit junk it still remains in the Task Scheduler.
You might also want to try Hiren's boot cd and the program rufus. If you want to create a USB boot drive that you can actually run to use as a tool for troubleshooting a system they are a great way to go. Here is a link to a video on youtube I made describing how to create the drive...
Here is a video I made showing how to boot directly to the desktop in Windows 8.1.https://www.youtube.com/watch?v=8D12kNxXLws
Here is a whole playlist of both Windows 8 and 8.1 videos.
Here is a video showing how to have two apps side by side in Windows 8.1
Here is a video on how to close an app in Windows 8 or 8.1.