i have read all 23 pages of this thread, downloaded a few tools (nand compare, nandpro 2.0b, findsecdata), and started my HDD restoring, without any previous knowing of dumping and all that stuff.
i dumped nand 4 times before getting 2 good dumps.
I used nandpro 2.0b and since i have a Falcon Board 3.0 which is 16mb i typed
nandpro lpt: -r16 nand.bin -1st dump
nandpro lpt: -r16 nand2.bin -2nd dump
nandpro lpt: -r16 nand3.bin -3rd dump
nandpro lpt: -r16 nand4.bin -4th dump
after read ive checked them in nand compare i got this:

this means that two dumps match, remember to do that before writing back to console. this was my 3rd and 4th dump. first two dumps were bad because i surfed the internet and downloaded some stuff at the time of reading so my advice is, leave your pc alone while reading nand, turn off all your messengers, downloaders and stuff and leave it alone to dump in peace

also as you can see on the picture, you can reconstruct 3rd nand from 2 bad ones, cause probably errors arent the same always, but i cant confirm that this will give you a good dump cause at the end i got two good ones.
after that ive started findsecdata on my nand4.bin and got this:

so i typed recommended commands:
nandpro.exe lpt: -w16 Patchedsecdata024C.bin 102 1
nandpro.exe lpt: -w16 Patchedfiletable0103By00F7.bin 103 1
after that i unhooked the cable from pc but left it on mobo just in case i didnt repaired hdd function, turned on the xbox, inserted disc and tried to install. and this was the result:

i believe i was among the lucky ones to easy get the positive result considering what problems do ppl have with this (yes ive read all 23 pages

), but i just wanted to share my experience with noobs like me and prove that for restoring hdd functions you only need 3 programs (nandpro 2.0b, nand compare, findsecdata, no need for hex editing). this can also serve like some kind of updated tutorial, and at the end i want to thank boby2pc the most, for making such good program, and also this forum, forum xbox scene and xboxhacker.
thank you all and now im goin to enjoy playing games from HDD
cya and good luck with restoring your HDD functions
Akiris