Type the following commands in Terminal:
defaults write com.apple.Finder AppleShowAllFiles YES
killall -HUP Finder
The first command sets a hidden preference so the finder shows all files and the second command restarts the Finder so these preferences take effect. The kill all command tells Finder to quit while the -HUP flag asks the program to restart.
The files can be hidden by typing the following into Terminal:
defaults write com.apple.Finder AppleShowAllFiles NO
killall -HUP Finder
If these commands do not work try a lower case F in the word Finder in the following command:
defaults write com.apple.Finder AppleShowAllFiles
