Dave, obviously paul wasn't aware he had a virus and infact that email could have come from ANYBODYS machine who has a virus AND yours and pauls email addys in thier email list.
looks to me like someones machine is infected and is spoofing peoples email addresses, I have had a few lateley from names i recognise on PassionFord but i dont actually know them.
Easiest thing to do is NOT OPEN EMAILS FROM PEOPLE YOU DONT KNOW especially if they have an attatchment with them, which is common sense really.
hope this helps.
oh and run a virus check peeps as it could be anybodys computer that these are coming from