I'd be concerned about an auto save crashing the program. This likely indicates something buggy in your computer that's going to lead to more serious problems later.
That said, you can turn off auto saving by unchecking the option on the Auto Save page of your Preferences. (Preferences are under the Edit menu on a PC.)
But as I said, if the problem is crashing doing something as simple as outputting a half hour MP4, it might be worth looking deeper into what's causing this instability. The program should be able to do this without even working up a sweat (assuming your computer is up to snuff).
I've used Premiere Elements on all 3 of my computers (the one I'm using is brand new and works flawlessly on everything except Premiere Elements) and it's always been insanely buggy. Everyone I know that has it has said that it crashes A LOT and has the same problems as me. Not a big deal imo; just thought I'd let you know that (from my experiences) it's not a rarity. Thank you for letting me know how to convert the video!
... Everyone I know that has it has said that it crashes A LOT ....
Everyone that I know that uses it says it runs fine. In five years of using four versions on three computers, I've not had it "crash" once.