I've been working for the past two days trying to get SIMS 2 operating on my PC using Windows XP and encountered the same problem(s) as many others with DirectX9C. But today, I was able to get it running! So for whatever it's worth, here is what I did.
After installing a DirectX9C compatible video card, I received the error message that the "cabinet file for installation cannot be trusted". I then downloaded the SP2 service pack 2 from the Microsoft website because it had the DirectX9C. SIMS 2 appeared to have loaded but when I tried to run it I received an error message stating that it "failed to find any DirectX9C graphic adaptors...". After running a "dxdiag" ("START", "RUN" type "dxdiag" and "OK") I confirmed that Direct9xC was loaded; however, under the "Display" tab I noticed I did not enable the "DirectDraw Acceleration", "Direct3D Acceleration", and "AGP Texture Acceleration". After enabling these features, SIMS 2 became operational.
I hope this helps some of you out because I was just about to give up.