There used to be a program called "End It All" that diabled Nortons and all the other programs that run in the background and affect the way the Sims runs. That might be what's happening. My 13-yr-old accidently downloaded adware (virus!) to my laptop. I have downloaded spybot to get rid of it, but so far no luck. I have to disable it every time I start up the computer. I will delete it, but it has a self-replicating program that you have to remove manually if I understand right, and I can't figure out how to do that. Anyway, my point is that maybe you have something like that on your computer. My son didn't even know he had downloaded it. He clicked on a pop-up on an online gaming site and it put this whole "search-engine/spam virus" onto the machine. When you have nothing running right after start-up, do alt/ctrl/delete and look at the running programs.
yeah, spyware can be evil... have you tried spyware doctor? it works pretty good for me, it found & eliminated about 40 spyware items on my computer a couple of days ago... try this link if you'd like to try it out: http://www.download.com/Spyware-Doctor/3000-8022_4-10293213.html i get all my programs from download.com... they have a great app search engine...
If you know where the file is but can't delete it due to "Access denied: application still running" or some other crap like that, the solution is to use the all-powerful Safe Mode.
For anyone who searches Ctrl shift and c and comes across this thread read my signature and it will tell you how to get cheats working !