Following Axels advice I've upgraded to Windows 7 to gain full benefit of FPV and I've put the OS, FPV and IMatch on a 60GB SSD.
To my surprise FPV browses Tif (canon RAW) files seemingly just as fast as any other type of file.
But Tif files are imbedded with a very small jpg so I don't think FPV is reading this and the browsing speed seems far too fast for a full RAW conversion.
I thought naively that the secret was the 2.4 codecs but Windows, Breeze Browser (still needed for key wording) and IMatch still show a very small image. Any ideas anyone how its done and is it something that could be integrated with IMatch.