Google is your friend, embrace him warmly!
http://www.google.com/search?hl=en&h...o+disk&spell=1 Specifically, this might help:
http://support.its.ied.edu.hk/stufaq/5.56.html.
However, before you do the above, you might want to back up your registry first:
http://service1.symantec.com/SUPPORT...rc=sec_doc_nam