Minecraft Forums

I'm quickly finding more mods from older versions I want to use, and don't always want to redownload all my mods when a patch comes out. So the logical thing is to have multiple versions of forge to play with right? But when I tried to download two different versions it crashed...it tried to use the wrong libraries since it didn't download it's own. Is there a proper way to do this, or a program that will allow me to?