Vista holds the boot critical files which need to be moved to Win7 first.
Please post back a screenshot of your full Disk Management map so we can advise you of the specific steps to achieve what you want. Use Snipping Tool in Start Menu, attach file using paper clip in reply box.
Study the files in your Win7 root with file view set to Details to see what is there. Look for windows.old, which is the entire previous OS files if you clean installed from Vista? You can delete it using Disk Cleanup after retrieving all needed files.