So, I was having all sorts of problems installing my win 8 upgrade on my new XPS one 27 machine, and spent alot of time on the phone with Dell trying to get this fixed..
Turns out that Microsoft and Dell have set up a dedicated hot line for Dell XPS owners having issues with their install..
I dont have the number, but if you call Dell Tech Support, they should direct you to that number, if you are having problems installing win 8 on your XPS machine...

BTW, I got Dell to take back my new XPS, and exchange it for a win 8 version, with touch screen!
I have to pay the difference, which is fine, but it was past their normal 21 day exchange time frame, so kudo's to Dell for stepping up to the plate!