Morning boys & girls

A question for you...
If you have an off the shelf PC or Laptop that came with "Vista Home Preium - 32 bit", but you install "XP Home - 32 bit". Can you use the Vista licence number on the XP instalation?
The fuller story goes like this. My brother got a refurbbed ASUS laptop from Dabs, as he needed one for work (very few schools are MAC savie). But as seems to be the fassion at the moment with manufactures, they carve the disk in half and stick the "recovery data" on the other partition. For some odd reason thay don't want to give you any install media. Because of course hard drives never go wrong. Moving parts will never screw up. But by the by, the current lay out of the hard drive sux.
So the idear is that it should be possable to downgrade. I know for work we stick XP licence lables on tills running WIN NT. So I think it should be possable. Unfortunatly I can't make heads or tails of the Microsoft WEB site. And googeling the question doesn't seem to give me the answer I'm looking for. I figuered out that it can be done on the Ultimate and Buissness OEM Vistas. There are even some walk throughs on using the recovery console. But there is nothing that says either "yes" or "no" to where it is possable to take a blank or formated drive, install windows XP home and when it asks for a licence number, use the code from the OEM Vista Home Priemium sticker. And then activate OK.
What do you recon? Any one tried this, know anyone that tried this. Did it work? Will it work?
Worse case senario I'll have to tell him that he will need to go and buy and OEM copy of XP and use the licence key that comes with it.
On a slightly side note. Does any one know if it is possable to get a hold of just the instalation disk for Vista Home priemium? Do I need to talk nicely to Microsoft and tell them I'm a system builder and that I'll buy licences off them as I need them?
Questions questions
