Yes, it is no fun when you're all excited about a game you waited to play for almost a year, and then BAM you can't play it. Unfortunately this is due to your hardware system requirements within the program itself.
I will tell you now that I have 4GB RAM, Quad Core Chip, 512 Higher End Video Card. I can play the game just fine.
My second computer has 1.5GB Ram, Single Core 3GHz, 256MB Video Card, and that also plays the game, but a wee bit slower than I would like.
The Sims 3 game box tells you what Video cards work and which do not. I'm sure the website also offers more information on the game requirements and which video cards work best.
You or your parents can easily look up your computers Motherboard to find out what memory and video you can upgrade to. Example at TigerDirect.com you can now get 4GB Ram on sale for around $35.00. You can get a 512 to 1TB video card (low-mid range) for around $80.00. It might be worth upgrading if you're truly a Sims fan.