So to do this do you then actually have to , as in my case reload Xp first and then load W 7 ?
Howdy.
XP users are in a slightly different situation as there's no upgrade path from XP directly to Windows 7 so you're not in a position to be able to buy an upgrade license, unless you also happen to have a copy of Windows Vista...
The installs are actually the same, i.e. the files on the DVD are identical, the license key dictates which variant you'll be installing and also whether you're doing an upgrade or a clean install. Just to muddy the waters a little, you can't upgrade any old Vista variant to any old Windows 7 variant either. The upgrade paths are fixed, you can't upgrade Vista Home Premium to Windows 7 professional for example.
Edit: I should add that the actual installer won't stop you from doing an unsupported upgrade, but your key won't activate.
Microsoft, it seems, have learned the lession of Vista whereby people were buying upgrade licenses at half the price and doing clean installs anyway.