In May 2009 I bought a Hewlett Packard Desktop PC, a Pavilion Media Center with Vista x64 installed. It has 2 hard drives installed, and I would like to either install Windows 7 on the other hard drive since I have the HP factory recovery partition and CDs for both Vista x86 and x64. Can I buy the Upgrade version of Windows 7 and install it on this Vista PC if I have the Factory version of Vista, or do you have to have the retail version of Vista in order to get an Upgrade version of Windows 7?
Here is the reason I am asking. Back in 2001 I had Windows ME on a new HP computer. I bought the Windows XP Pro Upgrade CD and installed it, and it let me keep my files and folders from ME, and I used XP for 8 years. Then my C:\Windows\System32\ Master Boot Record files and several other important files were lost in some sort of incident I can't fully diagnose, and I was unable to reinstall Windows XP, because it said I did not have a verifiable version of Windows. It asked for me to put a Windows CD into the CD-ROM drive, and I put the factory CD into the CD Rom drive of Windows ME, and it did not accept that as an acceptable Windows ME CD, maybe I needed to completely wipe the drive and install Windows ME before it would have worked again? I was trying to do the System Repair procedure it was offering for me to do, but it clearly didn't work, but 9 years of my life are on that old hard drive, I just have to find someone who can recover it, when I have enough money to pay them to do it. Ironically, I was in the process of uploading the files, photos, etc. to Carbonite online backup service and had just purchased a Firewire/USB/eSATA external hardrive triple interface when it happened, and I blame the beta Carbonite online storage service which came with the external drive for a year free, for the attack on my hard drive.
In summary, can I buy the less costly Windows 7 Home Premium to Upgrade my Vista Home Premium x64 Desktop PC with the factory version installed on it, or do I need to buy the more expensive "full" version of Windows 7 since I don't have a retail version of Vista?
Thank You for answering my long winded question.