I was trying to clean out my system with stuff that had been installed or downloaded that I didn't need. Well, now I get these blank boxes with little red x's in them and before I did not get these. What did I erase on my computer and how do I get it back?

Details aren't possible without a more detailed description of what you are attempting to view when the red "x"s appear. Many Windows OS (operating system) functions utilize portions of Microsoft's Internet Explorer web browser even when the Windows function doesn't require an internet connection. Internet Explorer displays a red "x" when an image (usually a .gif or .jpg file) isn't available where the browser expects the image file to be. Apparently you have deleted some of those image files. Availability of the particular files you deleted varies depending on what provisions your computer manufacturer provided for recovering a damaged OS.