missing tree command

Please read this:

http://ubuntu-virginia.ubuntuforums.org/showpost.php?p=6762856&postcount=6

The tree package (containing the tree command) should be in the Universe repository.

You can get a listing of directories similar to the output of the windows tree command with help of the find command which is far more powerful than the tree command (but has a more complicated syntax to use)

The equivalent to the command 'tree' (give a listing of the directory tree) is
find . -type d -print

The equivalent to the command 'tree /f' (give a listing of the directory tree with all files) is
find . -print

(You might want to add 2>/dev/null to each of the commands to eliminate warning messages about e.g. missing access rights)

All details about usage and parameters of the find command can be found in the man pages.