[rustydog]

First, I wish to thank all of those who have provided valuable information to my questions. Those responses are sincerely appreciated.

Basic Upgrade. From Professional to Basic using the Basic Upgrade retail disk. Skip all the reasons that this is not a wise idea, for now.

I have read all over the place why this can or cannot be done. I think, some are stating that they have 'built' a system with XP and have a retail disk version of XP. As I read that one has to insert the XP disk after or during the insertion of the Basic Upgrade disk.

All the systems that I see are retail desktops from Dell, HP, etc. I don't think any of them provide an XP disk anymore. I think they just gave some sort of 'restore' disk or disks. Restore might be the wrong word, maybe, it is a 'reformat' disk - or whatever. But it is not a retail version of XP with a product code (as far as I can remember).

So, on a system like above, running XP Pro. during the 'upgrade' process, is MS going to ask for the KEY to the XP? or just he key that comes with the retail version of Vista Basic - or both product keys?

And what if: OK, say running XP Pro. and put in the Basic Upgade disk, and something goes wrong. Does one lose both XP and Vista? Or will the system just reject Vista and revert back to XP?

Again, does one need just the product key for Basic or both the product keys to XP and Basic? And, running XP Pro. if one does not have any key to the XP, what happens. And finally, does one need the product key to XP doing a Basic Upgrade or is just the Basic product key enough?

From what I have read, all of this is going to be a 'clean install' using the Basic Upgrade retail disk.