Fat Guy in a Little Coat

How do you unvolunteer yourself from a goodwill action by someone? A family relative recently purchased a new TV and I off-handedly inquired about the "old" TV. Before I knew it, we'd been selected as the new parents of a 45" Hitachi projection TV. The only problem is that it is HUGE in our rather small living room -- a fact we didn't totally realize until it sat down in our living room -- and I don't know how to "tactfully" unvolunteer ourselves.