Hi, welcome as I am a new member also. I have upgraded from Gingerbread to Ice Cream Sandwich 4.04, but following procedures should work.
Go to Google Play and install a free program called "Task Manager". It lists all running apps and kill your selections.
Hard press right menu button. Go to Settings/Apps and select "Running". Open running app and press stop. Done!
Hard press centre Home button and hold for a few seconds. A menu appears with all running apps. Long press your selection, until a menu pops up. Select "remove from list". Done!