not working with my i tunes files...

i uploaded the new i tunes and much to my dismay i cant use 80-90% of my music. the bottom of the screen starts blinking and then says file not found. i put a lot of money into my digital collection. any help or suggestions would be great.

Hello,

You have propbably a change in your default iTunes location, you must update it.
Click on iTunes menu > Preferences > Advanced, and check the setting iTunes Media Folder location.
If it doesn't fit with your actual folder location, click on change, and show to iTunes the folder where your iTunes music files are located.