Choly
So sorry you are having problems. But, I don't think you need to panic about the games not working.
Sadly, from what you say, I think you have peobably lost your sim. Why don't you put it down to a learning experience and start a new family? It's worked for me in the past:)
Might I suggest that you do a Factory Reset, See the stickies in technical help.
Then always use the "save as" option when saving your game. That way, if anything goes wrong you can always revert to a previous save. I'm over careful
I make my new game and save it as xxxx start (example: IP start). then my next save will be xxxx 1. I do this up to 6 then return and overwrite game xxxx 1 etc. So, I always have my starting game and six saves available. I always save this way prior to going into edit town, or going on a WA trip, or whenever I am about to make a major change in my game like getting married for example or moving in another sim. I know its not like real life
because if I don't like the change, I can just go back a save or two! Wish real life was like that, no first husband for starters:). Changing the single number at the end before completing the save is very quick and easy, you won't even have to think about it after a while, it becomes a habit.
The easy way to back-up your saves prior to installing a new EP is to create a new folder on your desk top ("sims saves" or something similar). Then go to your Documents folder, Electronic arts, The Sims 3. In that folder you will find a folder called Saves. Copy this folder to the new folder on your desk top.
Good luck and happy simming.