One last point I got an email from someone today saying I sent them a infected email, so I again check my system and it is clean.
There probably isn't anything you can do about this. Many of the new email viruses will grab every email address on the infected computer and then use random combinations of the addresses for the To and From fields in the emails they send out. The email the person was complaining about could easily have come from a friend's or family member's computer, or someone else's computer that they forwarded an email to.
I was in a similar situation last year, but was able to track down where the virus was coming from (my cousin and her friends had been infected), and stop it. If the emails are coming from the same address you could block it, but otherwise you can't do much. Keep your anti-virus software up to date, use a firewall if you don't already and run Spybot or AdAware, or both, occasionally and your computer should be fine.
goates