I take it you're using either AOL 9.1, AOL Desktop, or AOL webmail. If so, you cannot turn off auto-quoting of messages on reply. You have a few options:
1) Use AOL 9.0
2) Use an e-mail program that gives you a choice (most do)
3) Type CTRL-A in your reply to highlight the quoted text for easy deletion (this may not work in webmail)
4) Highlight a single word in the message before clicking reply. This makes it easy to remove the quote from your reply. Again, this may not work in webmail.
5) Live with it. ;-)