lilah012 - There's nothing special about the Dell Inspiron 1501 operating system that would make an os update for it do something that an os update for another computer wouldn't do. That said there very well be some update that happened recently causing this because you are the 4th person in maybe 2 weeks to report it. If it doesn't matter what operating system you have then maybe it's a driver or some other unnecessary add on like that stupid Silverlight thing I keep getting a popup for. However as you can see from reading this person's thread the update was not connected to the operating system because running ts2 on another user account fixed it.

What have you done to try to fix this? There are -a lot- of suggestions in this thread?

You're probably right about the laptop model not making a difference. It was just that when I began Googling "sims 2" with "dell inspiron 1501" I suddenly got a lot of results.

Buried further in the Google results, I found this:
http://community.livejournal.com/thesims2/5320873.html

And it worked! Although I'll add another step that I did...

After I downloaded and installed the BIOS update, I then uninstalled my Synaptics touchpad driver. (Control Panel, Hardware and Sound, Device Manager, Mice and Other Pointing Devices, Synaptics PS/2 Port TouchPad, Driver tab.)

After I uninstalled it, I then went back to the Dell Support page and downloaded and installed the Synpatics Driver from Input Device Manager(s).

So... I don't know if this will work for everyone, but this was the only thing that worked after I had disabled my touchpad, did a custom system restore (I believed at one point that Microsoft's updates did something), and the usual Sims stuff, like patching and custom content issues.

The update people are complaining about may be a touchpad driver update through Microsoft.. I have had Microsoft updates try to update drivers on various hardware incorrectly many times before. I recommend never doing driver updates through Microsoft for this reason. Synaptics touchpads are very common, so this is good information to have. Thank you for sharing, and glad you got it fixed.

I had this same proem with my game for about 2 months. On day I decided to mess around with the laptop and I took out the battery for about 5 minutes. I reconnected the battery and decided to try the game again. It worked perfectly.

So my suggestion is to disconnect the battery. I don't know if this was the problem but It worked for me.