Well, The reason I suggest learning C is because it uses "real" data types. Whereas C++ has all this bullshit like strings, which lead beginning programmers to believe there is such a datatype... And there is not. So thats why, imo, I suggest learning C.

As for audio programming, that can be pretty complex depending on the file format you want to edit. What exactly were you trying to 'edit'? (File format, and what about the file?)

For your backup program, I suggest performing a checksum on the files, and you can compare the checksum, and normally files will not 'collide' and you can tell if they are different files by comparing the sums. Modified/accessed dates can be altered/invalid/missing/etc. And not all "edits" will increase the file size either. Although once you find that the file is indeed different those might be handy to look at if available. See http://msdn.microsoft.com/en-us/library/ms724320(VS.85).aspx for more information on how to call GetFileTime. Also, you don't need to choose a strong checksum that can be slower to calculate -- CRC should be good enough.