You don't need to recopy everything. If you know where the files actually are now, you can use MC's "Find and Replace" function to do what you're attempting.
You select all the files that are showing as "unlinked," right click, then select Library Tools/ Find and Replace. Select "filename (path)" from the list, then enter the old path in the "find what" window, i.e. the one that the files CURRENTLY show, which is the "incorrect" one (just enter the path that's common to ALL the files, not the entire filename.) Enter the "new" path in the "replace" window -- this is the path to where the files are actually located now. (This might be as simple as changing the single drive letter in the path -- I don't know if you've made any other changes to your directory structure.)
When you hit "Okay," MC will restruture the list to reflect the new path to the files. The message will tell you if and how many changes were made. If it says "0" files were changed, you need to play with the settings and what you type in the windows.
Just in case I might have misunderstood some of the specifics of your particular case, you might have to play with specifics of what I said above. From your description, however, it sounds like the Find and Replace function will in fact solve this issue for you by simply renaming the path to reflect the new location of the files -- and it's a LOT faster than recopying everything.
Good luck,
Larry