Freezing & Crashing to Desktop with "The Sims 3 has stopped working" error message

Okay, seeing as I was having difficulty installing the game on my mac, I decided to try my luck on my brother's PC. I followed the Ultimate Guide and installed the base game plus all of the main EPs (except Ambitions) and applied the manual patch and the ultimate fix. Everything worked fine until I actually started to play the game. I could play for about 20 minutes before the game crashed to the desktop and I got the "Sims 3 has stopped working" message.

I tried deleting all the cache .package files and the Current Game folder contents and the Thumbnails folder contents, to no avail. Then I tried changing the DEP settings. That was all fine until I tried to add the following files:

- Sims3LauncherW.exe for the Base Game (C:\Program Files\Electronic Arts\The Sims 3\Game\Bin\)
- Sims3Launcher.exe for both Late Night and World Adventures (C:\Program Files\Electronic Arts\The Sims 3 World Adventures\Game\Bin\) and (C:\Program Files\Electronic Arts\The Sims 3 Late Night\Game\Bin\)

I got a message saying:
"This programme must run with data execution protection enabled. You cannot turn off DEP for this programme."

So yeah, that leads me to believe that that may be my problem? But I am a complete computer n00b and don't know what to do about that...

Here are my PC Specs:
Windows 7 Home Premium Service Pack 1, 64-bit
AMD A8-5500 APU with Radeon(tm) HD Graphics 3.20 GHz (with Peformance rated at 7.2GHz, whatever that means?)
AMD Radeon HD 7560D
3.6 GB RAM
726 GB Free Disk Space

Games installed:
Base Game
World Adventures
Late Night
Seasons
Pets
Showtime
Supernatural
University Life

I have no downloaded CC or Mods installed (or even in the folders).
If you need any more info, let me know! Thanks in advance for your help. (:

That is fine, you cannot add those to the DEP anyway.
Don't worry!
According to here, your cards aren't fully supported... So lagging might still be here whatever you try.
Anyway, run your game on the 5500, which is better for your game!!

Oh, that's good! (:
Lame ): I used CanYouRunIt to see if I could run the EPs and it gave me the all-clear. ):
Also, yeah, mentioned I was a total PC n00b... How exactly do I run the game on the 5500? S: Sorry!

Sure no problem!
You have the correct requirements, but some are in Maybe: your game will run, but not as smoothly as it could!
You can find your card (search bar), then in options you can probably customize for your game (sorry, I don't have this card, just try and tell me if you need help!)

Okay, so I talked to my boyfriend, who has an infinitely greater knowledge than me when it comes to all things technical, and he told me that there isn't actually a dedicated card, and that the onboard card is the 7560, even though it says 5500 in the system info, for whatever reason? So yeah, I have no option but to run it on the 7560. That, or get a new card. ):

Since posting, I've tried all of the relevant options on the crashes fix page (https://games4theworld.forumotion.com/t857-the-sims-3-crashes-freezes-to-desktop-fix-updated-on-29-09-2012) with no luck. ): The game still crashes after about 20 minutes, every time.
Haven't tried GameBooster yet, but I'm not feeling particularly optimistic about it. Any other suggestions would be greatly appreciated if possible!
Thanks for all your help everyone!