Outlook Express 100% CPU

Recently I find that from time to time, MSIMN is using 100% CPU Deleting Ouitlook Express makes no difference but deleting MSIMN immediately solves the problem. I have no viruses, worms, Trojans, Malware, Adware or Spyware. I run Windows XP Pro on Athlon 2000+CPU, 512 mbyte ram. I compact O/E folders frequently off line and it takes only seconds to complete this. Grateful for any suggestions after the moronic replies I received when posting this problem to the official Windows XP newsgroups.