PGP 6.x and 7.x does not clear Windows alternate data streams that are attached to files on NTFS file systems, which allows attackers to recover sensitive information that was supposed to be deleted.
https://euvd.enisa.europa.eu/vulnerability/EUVD-2002-2048
http://www.seifried.org/security/advisories/kssa-003.html
http://www.securityfocus.com/bid/3912
http://www.securityfocus.com/archive/1/251565