I Need a Synchronizer

The proliferation of information is a botheration to me. I have now four or five computers with multiple copies of the same information on them. I don’t want to lose any of the information, in case it is ever valuable again (much of it is – pictures, music files, tests and questions for my classes), so I copy it and copy it and copy it, over and over again. So now I have multiple copies of each document, sometimes multiple copies on one computer. And when I try to copy over the old stuff, I first am scared to because of what I might lose – I have not composed exclusively on only one or the other ever. And I am second scared because when I try to erase them I am sometimes told that I cannot erase this or that “system file,” that some system file called “thumbs,” an unprepossessing name if ever there was one, might bring down all of Windows. I need a synchronizer, a program that will tell me about these various files, destroying the older identical copies and telling me the amount of variation betweten the mostly identical copies, maybe combining them into one document with the newer text, wherever it is, tacked on or interpolated into the old, pictured in red, or underlined, or preserved in speechclouds that can be called up at the asterisks that identify them, the old text shaded or parentheseed or italicized. There’s gotta be some way of organizing reams of virtual text without being swallowed up in the cataclysm of copies I’ve created.