It had no message at all. It just like nothing happened atall when I clicked itune icon.
Can you check something for me please?
Restart your PC. after the PC restarts, bring up your Task manager, and go to the "Processes" tab. Click "Image name" to sort the processes alphabetically.
Now try to launch iTunes.
Does an itunes.exe process appear? If so, does it vanish after a second or so, or does it persist in the Processes tab (even though iTunes itself never shows up)?