You can lock as many drives as you like.
On the xboxhdm disc you need the contents of your real C (i.e. you have to bypass shadow C before taking a copy), and the softmod dash files from E - \dash, \ndts and \NKP11
Actually, you're better off not re-using any of your current files. Get a clean stock 5960 C dash, make a softmod file set with Kingroach NDURE 3.1, and put them all on the xboxhdm CD in the appropriate places, along with your eeprom.bin. That way you can run the ndure script, to be certain that the fonts end up on the new disk in the right order.
Whichever option you choose, run xboxhdm, rebuild the disk, then run lockhd -a to lock it.