I'm doing this from memory but here goes:
1. Install the program in Windows
2. Create either a bootable CD or floppy image
3. Make SURE your external HDD is correctly connected and powered.
4. Boot from the now bootable device.
5. After the program loads, select the appropriate partition.
6. Either by right clicking on the partition or accessing the menu, there should be an option to recover or restore the partition.
7. After it says it is complete, make sure you save and allow it to write to the drive.
8. Remove bootable media.
9. Reboot machine.