and again it is certainly obvious that the solution is
reinstall from the original source
Could be
1 - the restore disks that came with the computer
or
2 - the iLife DVD that you purchased
or
3 - the app store - log in under the Apple id used to purchase the software or to set up the computer - look under purchases - you might have to unhide or accept the Application first
and it is not at all ovvious that you did look in the Applications folder before posting and it certainly is obvious that you have not actually resolved the problem by reinstalling as suggested
LN