For recovering accidentally overwritten partitions with TestDisk please follow these prcoedures:
- Stop using the drive!
- Boot Ubuntu live session ("Try Out Ubuntu") from a CD or USB-drive
- Install Testdisk to the live session via the Software Center
- follow this concise guide for recovery: TestDisk Step by Step
Optionally (but highly advisable) and if we had an external drive big enough to hold all of the faulty drive we can make a backup to recover data or partitions from an image. Make this image with the following command in a terminal:
sudo dd if=/dev/sdX of=/path/to/external_drive/backup.img
sdX with the drive to recover. Since
dd is an advanced and potentially harmful tool take extra care to not accidentally overwrite any drive you may still need.
In case you are unable to recover your partitions you may be able to recover single files by running PhotoRec wich comes with the TestDisk suite.
Just to have mentioned it: there are other "forensic" tools to help you recover lost partitions or files. See How to recover deleted files?.