The game automatically saves the last 12 or so turns so you can go back to one of those previous turns easely. You don't have to worry about manually saving or making multiple saves with different names.
If you want to go back some turns because the game crashes or you want to try a different strategy or whatever, just go to the load game screen, put the mouse over the game you want to roll back and follow the instructions that will appear on the pop-up window.
If i recal correctly you just have to hit the "home" key while pointing to the saved game you want to roll back. Each time you hit the key you will go back one turn.
By the way, is strange you have multiple crashes... have you patched up the game?