|Assuming this email is in your Inbox... Just delete it from your Inbox and your Deleted Items. Then, compact your pst file. It'll be gone from the pst file at that point.|
Or, create a new pst file and move everything from your current file into that one...excluding the email you don't want.
I am wondering why you are so concerned (paranoid?) about this one particular email.
Life is more painless for those who are brainless.