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#1
When you bought your computer it had an OS installed. If you read your manual, in the case of problem there is an f key, that can be pressed which enalbles you to return to factory condition,like the day that you received the computer. That OEM partition probably contains the original settings. Why is it empty? Probably when you did the upgrade the settings were erased.
Many may disagree, but I would do the install again, this time as a clean install. And delete the extra partitions, unless desired. When done you only need C: and one other for the backups, you actually can pick the letter.
As suggested, boot from the Win7DVD and select Custom install, then Advanced drive tools to delete all, repartition as you desire, then format before installing.
When the DVD boots up, it will read the prior OS and allow Upgrade key,.