Can't open Preferences System in Leopard

good Day everybody

Last night, i tried to switch to Mail , but i get a message error that said that it crashes on start up , so i tried to switch to iCal but it wont start too, and even for garageband iMovie iphoto iWeb , iDVD . Any of them would start up. I get a message error of crash. So i look for the console to see what 's wrong. And today i entered the preference system to change screensaver option and when i click on "Desktop and screensavers" i got the message error "impossible to load desktop and screensaver preference tab".

Process: Mail [1133]

Path: /Applications/Mail.app/Contents/MacOS/Mail

Identifier: com.apple.mail

Version: ??? (???)

Build Info: Mail-9360000~1

Code Type: PPC (Native)

Parent Process: launchd [61]

Interval Since Last Report: 86143 sec

Crashes Since Last Report: 16

Per-App Interval Since Last Report: 0 sec

Per-App Crashes Since Last Report: 5

Date/Time: 2011-09-22 15:08:21.807 +0000

OS Version: Mac OS X 10.5.8 (9L31a)

Report Version: 6

Anonymous UUID: 525A49FF-5106-4DD8-93A1-DC3CD3B34A12

Exception Type: EXC_BREAKPOINT (SIGTRAP)

Exception Codes: 0x0000000000000001, 0x000000008fe0105c

Crashed Thread: 0

Dyld Error Message:

Library not loaded: /System/Library/PrivateFrameworks/iLifeMediaBrowser.framework/Versions/A/iLifeM ediaBrowser

Referenced from: /Applications/Mail.app/Contents/MacOS/Mail

Reason: image not found

When i switch to GarageBand or iMovie or iDVD or iWEb , it says the samething.

Please any advice will be really really reaallllllllllly helpful. The one thing i would hear is that i will have to reinstall the operating system , cause i loose the DVD install of Tiger.