Error Message on System Preferences



I am a pretty novice computer user.

Last night I used the Pacifist program to try and go back to an earlier version of Quicktime (in order to use Flash). I was trying to replace QT 7.5 with QT 7.1.6.

Everything seemed to go smoothly (to my untrained eye), but now my Systems Preferences and Entourage don't work (error messages). I don't know what else, if anything, might have been affected. The internet still works, although the power icon in the upper right corner of the screen is also gone (along with whatever else used to be there).

How do I fix this--can I fix this?

I have a Macbook with OS X ver. 10.4.11.

Thank you for any help.