itunes and System Preference disappeared Somehow

[MrMacBookPro]

i Must have deleted something because i cannot open system preference or itunes..

When i try to open either of them a box pops up and says

"unable to open application. The application may be incomplete or damaged"

what do i need to do? thanks

 

[MrMacBookPro]

think i fixed it... I reinstalled the OS X recovery disk and everything seems to be working good so far..

can anyone chime in?