Red Flagged emails-Vista OS.

Using VISTA OS, I received a Red Flagged email. I wanted to Forward it on to someone else but without the Red Flag.
I cannot get rid of it (the Red Flag), but using XP (Outlook Express) I can simply click onto it (the Red Flag) and it goes away. Why anyone would bother using a Red Flag in the first place is beyond me, but I accept that it takes all sorts to make the world go around.
It (the Red Flag) has no purpose in my life, and it annoys the %^&* out of me if/when I get a Red Flagged email.
Has anyone got any advice for me as to how remove it bearing in mind I am referring to the VISTA OS?
My beloved XP has never caused me any problems. The Vista I use doesn't belong to me, THANK GOODNESS. I'm just trying to help others. They get the problems and phone me for help. I then tell them I shall ask A2K.