I finally found an old save file I thought I lost when I had to reformat my computer. My wife and daughter are getting into Minecraft now and wanted to show them the world I had spent so much effort making.
I think its from the 1.4 era (wolves had just been new). I drop it into my.minecraft/saves folder with the other worlds, and can see it. It says last played 3.31.11 and Must be converted!
However, when I select Play the game crashes out and when I select Re-Create the game crashes out.
I noticed that the folder with my world has slightly different files than the worlds I created via 1.7, but adding copies of those files to my old world's folder does not make it playable.