Q: how do i delete my i tunes library totaly so i can start again

That's pretty extreme. If you really want to start afresh, remove all the files in

Macintosh HD > Users > *User Name* > Music > iTunes

and put them in the trash.

If you just want to create a new library but keep your media, drag

Music/iTunes/iTunes Library.itl

to the trash and start iTunes.

What are the iTunes library files? - http://support.apple.com/kb/HT1660

More on iTunes library files and what they do - http://en.wikipedia.org/wiki/ITunes#Media_management

What are all those iTunes files? - http://www.macworld.com/article/139974/2009/04/itunes_files.html