The trouble is they don't tell you what the problem is. The MS website mentions a list of drivers none of which I have on my system. My PC is only a few months old and the drivers I installed for the printer, scanner, joystick etc were all the latest Vista drivers.Vista SP1 will not be offered if you have a potential problem.
Bearing in mind the problems MS intimate and the 434MB download I think I will hang on for while and see what develops.
Pete