could you open your finder and choose Go then Go to Folder and type in ~/Library/Preferences/ and click Go.
Find the com.apple.iTunes.plist file and move it to the desktop, then open iTunes and see if it works
Let us know what happens.
When you open the finder can you go to /Users/yourusername/Library/Preferences/
You should find the plist file there, If so drag it to your desktop.
If you cannot find it in that location can you do a spotlight search for com.apple.iTunes.plist and let me know where it is.
So are you clicking on iTunes in the dock to open it?
In tht case can you force Quit the application and move the oldand the newly created plist files to the trash then trash the program and empty the garbage.
Reboot your Mac and as soon as it starts to power pres an hold down the Shift key till you see the load icon then let go of the Shift key and wait up to 15 mins for the machine to Safe Boot, Whn you get to the login screen just choose reboot from the bottom o the window and then whenyour machine comes back up try reinstalling the latest version of iTunes.
Let me know what happens.