Actually, after reading few posts, I think I can update with xboxhdm by
0) extract xboxhdm zip file to a temp directory
1) copy/transfer my softmodded box epprom.bin, C and E contents to the unzipped directories in step 0
2) create iso file and burn it to cd-rw
3) open up PC connect cd/dvd drive to primary slave
4) connect the new blank hdd to primary master
5) change the PC setup to boot from cd
6) boot PC with the CD
7) At xboxhdm menu, select unlock hdd option

reboot the PC with the CD again
9) At the menu, type "xboxhd"
10) Select "build new xbox hd"
11) Select, "rebuild C" partition
12) Select "build F drive"
13) Re-lock hdd
14) Open xbox case and take old hdd out and replace it with the new hdd drive
Am I on the right track guys ? If not, anything else I should consider or missing ?
Many thanks