Is it appearing under Favorites, or Devices? If the latter, that's normal, and there's no way to change that. As long as the partition is mounted, it should show up there.
If the former, you could try deleting the com.apple.finder.plist preference file. If you're not sure how to get to your preferences folder, choose Go to Folder from the Finder's Go menu and enter the following path:
Find the file in that folder, move it to the trash, then log out and back in, and see if the problem goes away. If the problem remains, you can always move that file out of the trash and back to where it belongs, replacing the newer file that was created automatically.
If the former, you could try deleting the com.apple.finder.plist preference file.
Tried and failed I had a look through the Preferences for anything else, and found com.apple.sidebarlists.plist. Deleting this and relogging also failed to fix the issue.
I suspect the OS may be repopulating the contents of the plists in question using a cache, rather than creating a default file. Would deleting ~/Library/Caches/com.apple.finder/ help, do you think?
I've still got this exact same problem 4 months later. Steps attempted:
1) removing unwanted item from Favourites portion of Sidebar by dragging whilst holding Command then releasing, then deleting com.apple.Finder.plist and com.apple.sidebarlists.plist, followed by emptying the Trash.
2) deleting com.apple.Finder.plist and com.apple.sidebarlists.plist, followed by emptying the Trash, and then removing unwanted item from Favourites portion of Sidebar by dragging whilst holding Command then releasing
Whichever way I do it, when I re-log the user in question the unwanted item re-appears back in the Sidebar Favourites list.
Can someone help me get rid of this darn thing? It's just a drive partition, and it's superfluous in the Favourites portion of the sidebar because it already appears further up under the Devices heading.
Similar problem for me (Mountain Lion 10.8.2 on late 2011 MacBook Pro). Forum gurus should know that this thread is the first of at least three looking for a solution to this vexing problem:
Re: Can't delete item from sidebarand one I started:
No solution from anyone yet.
Two questions for Scotch_Brawth:
1) Did you ever try deleting ~/Library/Caches/com.apple.finder as you wondered about several months ago?
2) Does the drive partition also pop up in the sidebar Favorites whenever any other disk (external, internal, or DMG) is mounted, as it does for me?
(2) I hadn't noticed this before, but I've just tested it and, yes, the drive partition did re-appear after being deleted as soon as I inserted a USB flash drive!
And, now for the good news:
(1) I hadn't tried deleting this cache until you mentioned it just now. I just ran the following test:
Removed unwanted item from Sidebar, then:
Deleted com.apple.finder, com.apple.sidebar, and ~/Library/Caches/com.apple.finder, then:
Logged out and then back in again
The item did not re-appear in the Sidebar. I then inserted my flash drive, and again the item did not re-appear. I made a few changes regarding what I wanted to appear in the Sidebar (added a few things), and still the unwanted item did not re-appear.
I think it's fixed! Try this yourself and see if you get any success.
Holy cow! You found the solution, Scotch_Brawth! I trashed the three files you list and logged out, then back in. The partition was still there. Bad news.
Then I realized I had not emptied the trash before I had logged out. So I removed the item from the Favorites again, deleted the three files, emptied the trash, then logged out and back in. The partition was gone. I held my breath while I attached a couple of external drives and opened several DMG files, while making a number of changes to the items I wanted on the sidebar (both additions and deletions). So far, all is good! Thank you so much for persisting. You made my day ... maybe my whole New Year!