I have an OLD shower handle that is broken. I tried to turn off the hot water last night, but apparently broke something inside and now it won't turn off.

Here is a picture of what it looks like now: http://adamfwilson.googlepages.com/DSCF0581.JPG

The end of the extended piece (which I THINK is called the stem), has a number of straight splines. Turning this (with a small wrench) does not do anything.

How can I get that piece off... and how can I turn that particular facuet off so I can use hot water elsewhere in the house.

Thanks... and sorry for the rookie question!