Game breaks on loading. What to do?

If in danger or in doubt, run in circles, scream and shout. And reboot. And then, try these.

• The first thing you should always try when your game fails to load is very simple.
  Delete the files called Groups.cache, cigen.package and Accessories.cache located at: My Documents\EA Games\The Sims 2.
  These files can become corrupted stopping your game from loading. Its safe to delete as the game will generate a new one on loading. More information about this.

  After installing Free Time I seem to have to do this every time I run the game, or BodyShop, or HomeCrafter.

• It may be helpful to remove the contents of the SavedSims folder. 

• Delete the contents of the Thumbnails folder. These too will be regenerated.

• Another thing you can do is defrag your drives regularly. Note that if your game is installed on a drive other than C you still need to keep a reasonable amount of space on the C drive, as all Sims games create temporary files on C. The less red the better!
• The next thing to check is your downloads and skins. This is a time consuming business, and I do it in two parts.
  • I run Sims2Pack Clean Installer - get it here - this checks for any clashing objects. Doesn't seem to have a help file, but I delete all the files that show up in pink and anything that says Empty Package.
  • If that still doesn't fix the game, a visual check of the folders. My game simply does not run if it has .JPG, .ZIP, .RAR etc files in the downloads folder. EVERYTHING in there should be a .PACKAGE file. Even if it has a wierd numerical name.