I've found that Desktop searches, unupdated graphics card drivers and anti-virus or anti-spyware programs can all be problems. Also, close unneeded processes before starting, defragment your hard drive and check that there is a few GB of free space on it.
My computer has only 256MB RAM and a single 2.8ghz processor, running Windows XP professional and the Sims 2 runs. Slowly, but it runs.
I recently bought a(Don't laugh) Gateway GT5040 Media Center PC. It's a dual core with 2.8ghz ea. Plenty of DDR memory and all that. I also had an ATI PCI express 1300 radeon graphics card installed for games that my kids and I might play. The problem is, the only game that has the problem is Sims 2. It shuts down randomly in the middle of the game. I have downloaded the only patch for the game from the Sims website. Is this happening because Sims 2 is not compatable with Media Center Edition windows? Every other game we have is fine. I even downloaded the Age of Empires III demo to try and the PC didn't miss a beat running that game.
Any advice would be appreciated.