These are the specs per the Sims 2 site:
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Supported video cards (and the more video memory the better):
* ATI RadeonTM series (7000 or better)
o Radeon 7000/VE series (non-T&L; requires 2.0 GHz processor)
o 7200, 7500
o 8500, All-In-Wonder 8500
o 9000, 9200, 9500, 9600, 9700, 9800
o X300, X600, X800
* Nvidia® QuadroTM series
o Quadro, Quadro2, Quadro4
* Nvidia® Geforce series (GeForce2 and better)
o GeForce2
o GeForce3, 3 Ti
o GeForce4, 4Ti, MX 420, 440
o GeForce FX 5200, 5600, 5700, 5800, 5900, 5950
o GeForce 6600, 6800
* Intel® Extreme Graphics (non-T&L; requires 2.0 GHz processor)
o 82845, 82865, 82915
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Updating your video card software may help. The best way to do this is to check the support site for your video card's manufacturer.
Also, you may want to check and see if there are any updates available for The Sims 2 software itself as they may add additional video support.
I have a friend whose computer display regularly froze with the Sims / Sims2 and we ended up having to install a new video card, but you may have better luck.