I used Partition Magic software to reallocate partition space.
When I started Partition Magic, it asked to reset the partition drive letter and I responded "Yes" in the wizard. It changed the partition drive latter, but something went wrong and my disk partition is missing from my computer and I can neither access it with the drive letter nor see the drive icon.
I tried to change the partition drive letter using Windows 7 Storage Management, MiniTool Partition Wizard but could not reset the drive letter. I can see the drive in MiniTool Partition Wizard, Windows 7 Storage Management, but can not access it.