I have no experience with windows, but I suggest investing effort in evaluating an automated incremental backup solution. That saves space by only storing the files that changed, and the automatic part frees you from having to invent names (albeit that may be a downside, you can keep a text file with what has been done so far though, a change log, where the last entry would be equivalent to the name of the backup).
On a side note: compressing compressed files often is not really useful, so instead of raring mpqs, I suggest choosing a better algorithm for compression instead and only having one. Then again, the perfect automated backup solution would already do compression without you having to do anything.