So it sounds like the drive/drives are OK but the letters are muddled.
You can change the drive letters yourself - some instructions here:
Learn how to change or assign a Windows drive letter by using the Change Drive Letter and Paths feature in Disk Management.
learn.microsoft.com
Note as you're on 7 right clicking the start menu won't work if I recall correctly. What you can do instead to open Disk Management, is click start > run (or press windows key + R), then type:
diskmgmt.msc