I have and still continue to receive a large amount of emails or PMs asking me about clean installs using upgrade media and the legality. If you want the facts please look here:
 
http://blogs.zdnet.com/Bott/?p=1505&tag=nl.e539

What if you upgrade the hard drive, how does that work? The reason I ask is I have windows 7 and plan on upgrading the drive on this computer and moving this raid array to a different system. Can I simply remove the old drives, slap in the new one, and re-install? Or will I have to install XP on there and upgrade from there? Thanks all for your help.

Thanks for the link.

lascivious1

BOBMITCH,

i have a question or anyone that knows the answer i just started a fresh install and followed bob's directions and chose FORMAT and hit the OK button. did it format that quick? i just hit the button and that was it i never saw it do anything so i just chose NEXT and it started the install process? did i do something wrong or miss something?

all a quick format does is remove the first charecter of the files so they are not seen, and reset your alocation table, all the information is there but now windows knows to write over it when it needs to. That's why it's so fast, If you need to be sure it's gone there is a DOD wipe program that writes 1's and 0's over the information 7 times ( that way you know it's gone.) but that takes considerablly longer.

If you just want your upgrade CD to work and you are having any problems just use this guide from Paul Thurrott.
http://www.winsupersite.com/win7/clean_install_upgrade_media.asp

If you are at that point in the installation where it is time to enter the product key and you know you are entering the right key code but it won't take it returning an error that reads something like "not a valid key code" then M$ is searching for a previous installation and will not validate until it finds it. You are likely in the same situation I recently found my self in.

So, just a note here in hopes it will help someone out. First off I have Window 7 upgrade media on this machine and I recently lost a single hard drive of a raid array. Needles to say a format and reload was required once the new drive was replaced and raid rebuilt. Originally I had upgraded an XP machine but this install there would be no XP to upgrade. No problem right?..... You could install XP first however don't be afraid mother M$ will be there for you albeit a pain in the rear.

Proceed with installation as recommended by M$ and chose Custom when prompted.

At the point where you enter the product key don't bother it won't accept the key just click next with out entering the key and let the installation complete. Once at the desktop you will want to activate Windows but first you will have to call home. Remember in order to get all windows updates it will require an activated windows OS. When you make the call you will be asked a couple questions like is this copy installed on another machine and what happened to get you there but I did not have to prove I had XP or anything like that. The process is really quit simple and straight forward. The tech will have you initiate a program already on your machine "MSDT" and give you a 10 digit key code, at the appropriate time, that will allow your copy of Windows to be validated. With a quick restart you will verify Windows has be activated and the whole process will take you aprox. 10 minutes.

While on the phone the tech verified for me that any type of upgrade is supported CPU motherboard etc no problem. Furthermore he recommended that I keep the Case number to expedite matter in the future if need happens arises again. It's a simple process to reactivate the ticket and helps expedite the next go round.

Inconvenience aside it was painless really. The call was answered almost immediately too. The tech spoke English exceptionally well, was very friendly and very helpful. I must admit M$ has improved the experience and I didn't have to go through the hoops mentioned in the links above, ie: double install.
Quit frankly there is no need to "cheat", so to speak the system when there 's a much easier way.

I hope all you experiences with windows goes as smoothly for you as this did for me. Good Luck!

This Procedure is not recommended by MS, it does work I have used it twice.

1. Perform a custom clean install using upgrade media.
2. Make sure to deselct  Automatically activate Windows when I'm online
3. Open regedit.exe with and navigate to: HKEY_LOCAL_MACHINE/Software/Microsoft/Windows/CurrentVersion/Setup/OOBE/
4. Change MediaBootInstall from "1" to "0".
5. Open the Command Line Utility "Run as administrator".
6. In the Command Line Utility window, type: slmgr /rearm.
7. Close the Command Line Utility and reboot.
8. When Windows 7 reboots, run the Activate Windows utility, type in your product key and activate windows.

 If the procedure fails you will have to perform the "double installation".

They need to make it so that if you have an upgrade version, you can enter that key when installing it, then have it ask for the previous version's key.
 
IE I have windows 7, if I install from the windows 7  CD I should be able to enter the upgrade key, then have it ask for the vista key. that way it knows that you have both the base and the upgrade (and not just the upgrade) and you don't have to double install.
 
That's the way it should be imo, no need for any tricks.
 
Edit: and no, it's not thread necromancy, this is a sticky so it's alive, even if cryogenically frozen.