All credits for this *amazing* tool go to StackOverflow.
Download
What it does: Switches the Ace of Spades protocol (I think?) to a different game folder so you can have multiple versions installed at once instead of uninstalling, reinstalling, ininstalling, and so on.
How do you use it?: I suggest installing .70, saving it to a different location, then installing .75 (or whatever other version you want) and then saving that somewhere.
Once you have both game versions installed at once and in two different folders, run the EXE, choose which version you want to be opened with a server link, and save it. Then you can join a server for that version. When the time comes to switch versions, run it, choose the directory of the version you want, and save it.