Originally Posted by neogenesis
This has happened to me and I was able to resolve it. All I did was add the conflicted hdd to another running computer with windows. From here you can see both partitions and if it hasn't been formated, format it so both are active. Now through computer management I set both drives to a letter but assigning the partition I wanted "C:" to any letter that comes before the second partition letter.
Now stick the hdd into the original computer and windows will detect the partition with the OS from boot and automatically assign the drive to "C:".
Right there. You say format. Which means to wipe the drive of all info. Data lose.
Unless you mean change the properties of the drive to make it a active system drive. Which you can do with GParted or Acronis Disk Director as well.