I sincerely apologize if this was previously posted, but everything else I read on this, didn't help me the slightest bit

I have just gotten The Sims 2 Pets Expansion Pack off of eBay, and I feel I need some help. I want to start off by saying, I know a lot more about computers than most girls my age, but I'm still only 13, and have troubles. Okay. I've had The Sims 2 Double Deluxe for a while, and it works perfectly. I installed the Pets expansion pack, and now, after the movie intro, the loading page comes up (like it should). Then, the loading bar, just stops, I still hear the music, and then an error "ding" occurs. So, I pull up task manager, and I see an error message saying "The application has crashed. The application will now terminate" and my game closes. This happens every time I try to play TS2 Pets, and I really want to play it. My computer is a Windows Vista Home Premium (Service Pack 1) 64-bit with a NVIDIA GeForce 7100 /NVIDIA nForce 630i graphics card. I can't figure out what the problem is. My grandpa had a look at it, and he's kind of a whiz with computers. He asked me if the game only works for 32-bit systems, and my answer to him was "I have no clue". I used ATI to detect available driver updates, but it couldn't find any, and I've updated my game completely. And, yes I have tried reinstalling, and restarting my system. Can someone please try to identify my problem? Thank you

Pets works fine under either 32-bit or 64-bit OSes. Have you followed the Game Help:Game Problem^wiki FAQ? Problems which arise directly after installing an EP are usually caused by some CC which isn't compatible with the new EP, and this FAQ will help you identify the problem CC if that is the cause. In fact, even if the CC isn't the cause, the FAQ will help you identify what is.

That ding and crash as described in my experience almost always is due to incompatible CC.