Left over certificates

Giganews Newsgroups
Subject: Left over certificates
Posted by:  Gunna (Gun…@discussions.microsoft.com)
Date: Mon, 28 Apr 2008

I have a number of CA Exchange certificates in my issued certificates.  They
are all expired.  They have the message of "The certificate has a nonvalid
digital signature" Is this becuase they are expired?

Should I revoke expired certificates?