Many games, and from what I remember Sims is one of those, that will not load on a PC if the copy protection software detects a CD burning "UDF formatting" program, such as the Sonic DLA or Roxio Drag to Disc, Nero InCD on the PC.  If that is the case with your PC, temporarily uninstall that program and then after you have the program installed you can reinstall the DLA (or whatever you have).  Sonic DLA is mentioned as that is what comes with most Dell's that have a CD or DVD burner from the factory.

If this is not the case, suggest you repost on the Gaming section of the forum.  Or better yet scan or do a search for your problem on the gaming section as it most likely has been previously asked. 

Thank you!  I went to their website, and finally found the help section (it's rather complicated).  I tried a few things, and found something that worked -- I copied the contents of all four CD's to my harddrive, so it went smoothly from one CD to the next without having to stop.  That was the problem -- when it stopped for me to put in the next CD, it wouldn't start back up again.  But thanks anyway!