Your EEPROM data is actually stored in a chip on the motherboard. Some softmod installers extract this data to a file on your HDD so you can copy it somewhere safe. It would appear your softmod installer did not.
I would recommend resoftmodding with Krazie's NDure installer. You pretty much follow the same process as before, but this one should rip the EEPROM data as part of it's installation.
Alternatively, you could copy ConfigMagic to your console and tell that to make a backup for you. It'll store it on the root of the E partition.
The EEPROM data is used to lock/unlock your drive. The console won't boot with an unlocked drive.
Note that you could always hook your X-Box into a network with your PC. If you currently have no LAN setup at your house, just grab a great long crossover cable and string it between the computer and console. Then XBMC can play your videos straight off the computers hard drive, using a standard share.
Granted, though, the stock X-Box HDDs are tiny for the purposes of storing games...