Is it Windows 7 you're running? Here are some things you can do:
Run msconfig to stop any unnecessary programme's from loading up at the start. Windows 7 to go start and type msconfig in search prompt. With Windows xp it's something similar, can't quite remember, I believe there's a prompt line in the start menu.
To see what is taking up most of your pc resources you need to run the task manager. To do this press Ctrl+Alt+Del and select task manager. Go to Processes tab, then click on the CPU heading. This rearranges the items so that those using most CPU will be on top.
Windows update can be quite resource consuming in Windows 7 i've noticed, and I'm pretty sure it used to be also in Windows xp. Same with any other programmes that have an automatic update. If you can disable all those that should speed things up a bit as you won't have programmes constantly checking to see if they need an update. Sometimes my laptop will be running painfully slow just internet browsing (and I have a beast of a laptop), then all of a sudden it will speed up and run as normal, and I realise that it was the windows update.
What antivirus are you using? Some, like Norton, are notoriously resource heavy. If you are disconnected from the internet whilst playing the sims then you can turn off your antivirus and that should free up some more pc resources. Same with the anti spyware/adware. These two programmes will continuously run in the background checking everything so they use up valuable resources.
Hope some of these help, and that somebody else can think of something. But it does sound like you have some sort of background programme or task that is running and using up most of your pc resources. Especially if you keep your pc running clean from cache, cookies, temp files, etc.
Edit: TheChronicR beat me to the task manager bit. So, Windows 7 instructions, still type Ctrl+Alt+Del. Takes you to a screen (with blue background) with a list of options. Choose the last one 'Start Task Manager'.
Ok, pretty much at start up now it's my mouse, my internet, and Norton, plus EA. Not sure if EA needs to be in there but don't want to mess with it. I have everything disabled from there I can and start up is set for selective start up rather than the full start up.
Same thing with task manager. I remembered with Vista and XP you could safely shut off/remove anything labeled with your user name so did that. Wasn't that much there and very low cpu use but every bit helps.
What I have NOT been doing is shutting off Norton when I'm offline playing the game! DUH! I can't really change my Norton to something else as it is part of the cable thing that we use for internet but I can shut it off when I'm offline. Thanks for that tip! I had totally forgotten it. As for my spyware/adware thing, I shut it down after each time I clean out the pc. Disable it I should say.
So it is not running in the background at all. It's one of the few things I remembered from my Vista/XP days.
How/where do you shut off the automatic update for Windows? I KNOW that sucker is running because when I go to shut down at night it tells me to leave the pc alone it's about to update. Then again, how would you know when and if to update? Hmmm, I frequently get an update message from Adobe and Itunes/Quicktime as well, but no idea where to go to turn these off. I particularly get annoyed at the Itunes one as I do NOT want it to be my main music thingie. It's only on my pc to keep my kid happy buying the occasional song she wants for her IPod. I did not find these items listed in msconfig or task manager.
Thanks so much for the help. I'll actually be able to help my dh with his lap top as well. He is so leery of cleaning anything out then complains when things are slow.
Oh, would having a background on your desktop slow things down? I have a gorgeous screenie of the nectary remodel I did on mine. He keeps his desktop empty but he shares it with the kid and she is constantly changing "her" desktop. She's given up asking me if she can use my pc when I'm in the middle of a game which I pretty much always am if I'm not here. lol
Thanks again everybody. I'm going to go play without the Norton and see if that helps.