Hi, If you are using HP Vista, the HP Health Check also uses that combo.
To disable it, you'd need to change it (hotkey combo) through properties on the shortcut to none or change it to some other combo.
If you don't have that pgm. either, what happens when you are not in the game and you press Ctrl+Shift+C? If something opens, then that program is using those shortcut keys you'd need to change that program shortcut/combo so Sims can use it, etc.