I got a new graphics card (ATI Radeon 9550) installed Saturday and the graphics itself is amazing but whenever all of the settings are turned on high, it will cause the game to randomly freeze for no reason. The first time it froze after my sim fired the nanny. I haven't gone to that house since. Now when I'm on CAS, it freezes at random times now. One time it was when I turned the sim around. Another time, it was when I changed the sim's face templete to a new one. Many times it was when I tried changing the sim's eye color it freezes. I took off all of the downloads I got recently but that didn't help. Mind you, the game was working fine with all of my downloads on it before I got my new graphics card installed. Could I have gotten the wrong graphics card? The employee that I got the graphics card from and the graphics card box itself says that it works with my computer (Windows XP),so what is the problem?

How much RAM do you have?
What is your CPU?

TS2 is highly CPU+RAM dependent, the GPU is less used.

Uhh, what is CPU and how do you check how much RAM you have and your cPU? I'm not very computer-savvy. lol

Right-click on the My Computer icon on your desktop.
Select Properties.
CPU-central processing unit. Its speed is listed in on the general tab... in MHz or GHz.
Your amount of RAM is also indicated here... in MB or GB.

1.66 GHz and 512 of MB.

Upgrading your RAM to 1GB may solve the problem. I'm not positive that it's the reason your game freezes, but it would make sense to me.
Jordi or someone else may be able to say for sure.

Do I need to pay for this upgrade or can you just do it on your computer w/o any installment stuff?

You will need to buy more RAM. It's a piece of hardware for your computer that will need to be physically installed and not a download.

If you post the rest of your computer specifications (this faq will walk you through finding that information) then we can give you more advice on what kind of RAM you'll need: http://www.modthesims2.com/article.php?t=112711