Thanks Roncerr. I tried your suggestion but when in Programs and Features it wouldn't even give me the option to repair....only Uninstall/Change.
But the plot thickens! I changed ISP in Dec.2011. I now see that these messages that I can't ininstall actually go back to May 2010!!! They must still be on my old ISP's (Bell) server otherwise how could they now appear, apart from the fact that they would have been deleted way back after reading. I contacted Bell and they tell me there are "no messages in your mail box"!! Well they are certainly on my screen and I can't get rid of them!!