A couple tips:
With the latest version of
Kindle 4 PC - I was getting the "unsupported version" message as well.
Here's how I solved it:
- Uninstall the latest version of Kindle 4 PC
- Download Kindle 4 PC 1.01 Beta from here
- Disconnect from the internet (Otherwise, Kindle 4 PC will automatically update itself without your permission)
- Install Kindle 4 PC 1.01 Beta
- Run Unswindle
- Kindle 4 PC will automatically open
- Open the book you want to de-DRM
- Close Kindle 4 PC
- A Unswindle dialog box will pop up asking you where to save your decrypted file. Pick a spot.
- You're done!