If you go to this link http://community.winsupersite.com/bl...-answered.aspx
You will see many people discussing the upgrade disc installs. I saw someone posted this near the bottom of the page...
Here are my experiences trying to clean install Windows 7. First up is the successful try.
My home computer had Vista Home Premium 32bit installed on the C drive. I had 3 games installed on a 2nd physical D drive. I ordered Windows 7 Home Premium upgrade from Amazon.
Last night I, unplugged the hard drive containing the C drive. I unplugged the SATA cable to be exact. This left only the “D” drive which was not bootable. I booted my computer from the 64bit Windows 7 upgrade DVD. I choose the advanced install (or is called custom?). I formatted the drive. Windows 7 finished installing. I activated Windows 7, and even installed Microsoft Security Essentials which has its own check. There was no visible check for an older O/S. I didn’t have to put in an old media. There was no Windows.old folder to delete, just a clean install.
My other experience was with my work computer. I downloaded the Windows 7 Pro 64bit upgrade ISO from Microsoft’s eopen site. I burned it to a DVD using Windows 7 RC ISO burner. This DVD was not bootable. So I had to format my computer, install Windows 7 RC, upgraded to Windows 7 RTM, and delete the Windows.old folder. Before this I tried upgrading from Vista Pro 32bit to Windows 7 Pro 64bit and that didn’t work.
I had two different experiences with media from two different sources.
So the questions is…was my D drive that was part of a Vista installation but only had three games installed and no operating system enough to pass the upgrade check? If yes, then what was it about that drive that was enough? Or was there no upgrade check?