Not a whole lot to go on to begin with. First you may want to try a text mode install... boring, but more or less the same thing as the cutsie GUI menu but without the silly windows-esque slideshow. Or do you even get that far... I've never installed MD8.1 without having to use a boot disk.
Also, this might be the infamous Cable Select issue www.theregister.co.uk
was on about for months. What are the specs on the machine?
Hopefully this will make a start.