What version of windows do you have, and are you installing from a DVD or from a download?
If it is a download, are you installing from the original download, or have you downloaded it again?
For up to windows 7, have you tried http://support2.microsoft.com/mats/program_install_and_uninstall/en ?
Yes I did try this - no go!
Thank you
According to some of the reports on the web, a possible cause of this problem is that the file you are reinstalling from does not have the exact same filename as the file you previously installed it from.
An example given is that you downloaded it more than once and the downloader added a (1) to the end of the filename, either in the previous install or now. Apparently, microsoft remembers your filename and refuses to reinstall if the current and previous filenames do not exactly match.
I've no idea why it should do that and it sounds completely daft and irrelevant, but its probably worth trying the rename (and, if possible, running it from the download folder if that's where you are likely to have run it originally.