Sims 3 Crashes Computer?

I've been having a lot of issues lately with this computer. I had to reset everything because of a fatal system error, and when that didnt fix the error i had to take out the CMOS and put it back in, and that ended up fixing it. Before the whole reset, however, I used to be able to play the Sims 3 fine. It was a bit laggy, but that was because of the amount of space I offered it when I used to play it. It still played fine and I could play it as long as I wanted to with no real issues. Now, when I start up the sims 3, while its loading to get to the main menu the whole computer shuts down. No warning, nothing. When I looked in the event log it said that the cause of the shutdown was unknown or something like that. I've done this three times and each time I havent even been able to actually get into the game without my computer crashing.

Specs:
System
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Manufacturer Compaq-Presario
Model AY030AA-ABA CQ5320F
Total amount of system memory 3.00 GB RAM
System type 64-bit operating system
Number of processor cores 2

Storage
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Total size of hard disk(s) 466 GB
Disk partition (C:) 422 GB Free (456 GB Total)
Disk partition (D:) 1 GB Free (10 GB Total)
Media drive (E:) CD/DVD

Graphics
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Display adapter type ATI Radeon HD 2600 PRO
Total available graphics memory 1791 MB
Dedicated graphics memory 512 MB
Dedicated system memory 0 MB
Shared system memory 1279 MB
Display adapter driver version 8.850.0.0
Primary monitor resolution 1920x1080
DirectX version DirectX 10

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Im not very smart with understanding of any of these specs, so i just need some help.
Windows 7 Home Premium
nVIDIA GeForce

Let me know if you need anything else.

>Im starting to think that this is because of my power supply overheating.
>>UPDATE<< Replaced the power supply, still crashed