For some reason, Apple decided to make iTunes 10 interface vary a bit from the normal GUI. The Close, Minimize and Maximize buttons (the red, yellow, and green circles) run vertically instead of horizontally like the rest of the windows on OS X. Here’s how to fix it so it doesn’t feel abnormal.
1. Close iTunes.
2. Open Terminal.
3. Execute the following terminal command:
defaults write com.apple.iTunes full-window -1
4. Close the Terminal window and open iTunes. Your buttons will be back where they belong.