Windows 10 won't let me rename or delete certain folders

“Folder in use” and “You need permission” can have different causes. Taking ownership does not release a file held open by a program, and ownership alone does not grant permission to delete it.

Since you have already tried that, check the affected folder directly:

1. Find what is using it. Press Win + R, enter resmon, and open the CPU tab. Expand Associated Handles and search for a distinctive part of the folder name. If a recognizable app appears, save your work and close that app normally. Do not terminate unfamiliar system processes.
2. Check the actual permissions. Right-click the folder and open Properties > Security > Advanced > Effective Access. Select your account and view its effective access. Check Delete permission; deletion can also be allowed through Delete subfolders and files on the parent folder. Ownership and administrator status do not override every permission restriction.
3. Check syncing and previews. For a OneDrive or other synced folder, temporarily pause syncing. Close apps using its contents, turn off Explorer’s Preview pane with Alt + P, then retry.
4. Test in Safe Mode if it remains blocked. Save your work, hold Shift while selecting Restart, then choose Troubleshoot > Advanced options > Startup Settings > Restart > 4. Try renaming an affected folder there. Have your BitLocker recovery key available if device encryption is enabled.

If it works in Safe Mode, a background program is likely involved. If the permission error remains, focus on that folder’s access rules rather than repeating ownership changes.