Win7..upgrade or full? pls read for why I ask this

When I bought for myself I got the pre-release $99 deal Professional Upgrade version to upgrade my Vista Ultimate...now I know that it wasn't suppose to upgrade to Pro from Ultimate but I planned on a clean install and had a copy of XP I could use to show as the OS to upgrade.

This is what happened though: wiped my hard drive clean and started Win7 upgrade installation...installed as if it was a full version and never asked for proof a prior qualifying product. I have done clean install upgrade version before and they would normally ask for the OS disk from the OS to be upgraded but Win7 did not do that. It simply installed never mentioning anything about upgrading or a previous OS..entered product key and have been running it ever since the release.

I ask this because I am about to build a new PC for my step father and want to know what version of Win7 we should get for him...upgrade or full? He is using a copy of Vista on his machine that is his son-in-laws we believe and I want to avoid upgrading that Vista product key in case they have already done so. Basically just want him to have his own product key since we are not aware of the status of the key attached to his Vista...might have been upgraded already.

If we choose the upgrade version will it install like a full version like mine did or did I happen across some small anomoly that saved me a few $$?

It is my undertsanding and correct me if I am wrong on this that it should have asked for my Vista disk and then would have upgraded my Vista key and showed them I upgraded and then made my old Vista key null and void (not able to be used again)....is this correct? I did have the "system builder" version of Vista Ultimate but I don't think that had any bearing on why my 7 upgrade installation never asked about any previos OS and installed like it was a full version.

If we can save him $$ by getting the upgrade version then that will mean a few extra $$ we can put towards hardware and to be honest I know he has a copy of XP also but not sure if it is actually his either. They are all legal copies also just not sure if they are also in use by someone else as well...want to get him away from that finally.

If you have qualifying XP or Vista on hand, it needn't be installed to use Upgrade version: Clean Install with a Upgrade Windows 7 Version

The installer will see any installed OS upon bootup and pass a flag to allow use of Upgrade version key, even if you then use Custom>Drive Options to Delete, create New, and Format over the prior OS.

The installer hasn't asked for prior OS disk since XP.

It doesn't matter if the qualifying OS was itself an Upgrade, OEM or retail - although under the EULA a qualifying OEM only qualifies for the same machine and may not migrate as any other retail can.

If the VIsta Product Key is in question, audit it from HD using Belarc Advisor and keep it in a safe place in case activation should ever elevate to a MS agent during reinstall, and they should decide to start asking questions which they don't now. However, reinstalls are no longer necessary with built-in drive imaging that can reimage the OS to any HD in 15-20 minutes.

Right now on the Newegg wish list I am creating for him I have selected the system builder full version and that seems to be the best route for him since it is cheaper than the upgrade version anyways. He will have this new PC for a while a new OS will be out by the time he will be in need of a new PC so I think we will be straight.

I am still baffled as to when I installed my upgrade version of Win7 on a blank drive it never asked me to prove ownership of a qualifying product which I have of course. Unless the activation detected my previous Vista key in MS's database via identification of my motherboard. Like I said it never acted like an upgrade version in any way which I thought was odd and I mentioned this back at 7's release on here and nobody had any ideas then either. Maybe my Vista key is deactivated after all...doesn't matter though since it was used on this system but I do want to build a new PC soon and I still have to wonder if I can use my current copy of 7 on a new machine.