If you delete them all, at some point you'll probably regret it. The advice to bounce them all down to MP3 files and save em just so you can listen later without wasting massive amounts of hard drive space is a good one... Although it may not help you if 3 years from now you suddenly like one and want to recreate it... You won't have the building blocks any more, just the sound. Then you'd have to reconstruct it all which can be done but is also kind of tedious and time consuming. That being said, it's usually better to look ahead with your music creation than spending too much time looking back. You usually progress so quickly you won't even want to admit the stuff you made a year ago was you... Well that's my story most of the time, with only a few exceptions. For those exceptions though, I'm glad I have em in MP3.