I use a very slow old laptop to run my ubuntu system and frequently have problems with unresponsive applications. In Mac OSX there is a force quit menu that you can open to terminate any application, using a keyboard shortcut. The only similar application that I can find in ubuntu is system monitor and I cannot find how to add a keyboard shortcut for it. I have had several incidents where the entire system freezes and I can do anything except crash using the power button. Does anybody know of anything that might help? Perhaps something similar to windows Ctrl-Alt-Del?