When you get the Xboxhdm software, read the tutorial twice and then print it out for referal.
You aren't going to do anything to your original drive, so you always have it.
You have your C and E drives with the eeprom backed up to the PC, so you have everything necessary to recover with.
THE MOST IMPORTANT STEP: NEVER EVER TYPE IN THE PASSWORD TO LOCK THE DRIVE.
One typo and you are screwed. Use the eeprom.bin file and the software to lock the drive. I am having problems with Xboxhdm reading the eeprom off the CD, so if you have that problem, make sure you use a PC with a floppy you can get the eeprom onto and read from it.