There should be hotkeys in 7. if ctrl+z works, then there are shortcuts in there. ctrl+alt+z = Undo history crtl+shift+z = Redo history If those don't work you might be missing a config file (config? I'm not sure that's what it is). All you can do about that is maybe ask someone else who has 7 for thiers.
well that sucks... I went from 6 to CS since I heard 7 wasn't much of an upgrade. They might be set to binds already but you can't change them try pressing shift-ctrl-z (forward history) and alt-ctrl-z (backward history). hopefully they where not too lame and did not bind these for you already.