Is it true that one must use the exact same 8-Gig harddrive which came with the Xbox system originally. I thought the Xbox relied on the serial number information (or something like that) which told it the "true" harddrive was in there...... of course I could be completely wrong.
An unmodded xbox MUST have the same HDD and Motherboard. The drive itself is linked to the motherboard, so they must remain as a set. You can put any drive you want in a modded xbox. I believe there are also ways to put a different 8gig drive in a non-modded Xbox but you need to alter the drive to appear as if it was the original drive.
The DVD drive does not have this problem. You can swap in different Xbox dvd drives into non-modded systems with no problems.
As for the Samsung PC drives being Xbox drives.... no. There are a few specific models of Samsung PC drives that would work with an XBOX. They need to be modded, and are now discontinued. You CANNOT just go grab a PC DVD drive and swap it into an xbox as you need to alter the power cable.