I think you may be able to fix this by getting your hands on another EEPROM compatible with your version of Xbox. You can then make a bootable file of something like XBMC (need to rename the xboxmediacenter.xbe as default.xbe) and copy the EEPROM to a specific location on your hardrive (root of the C: drive). I'm not sure if XBMCs FTP function works whilst booted fom CD, I suspect it would, if not you may need to adjust network settings. If that doesn't work, add a folder (named whatever you want) containing the EEPROM.bin file to your CD when you burn the bootable XBMC disc. Once booted into XBMC, you should be able to navigate to it within the My Files option and copy it to where it needs to go.
Then you want to make a bootable cd of a program called EEPROMagic and use that program to restore your EEPROM from the one your copied to the C:. If all goes well you will then be able to boot into Xenium OS where you can then use the 'restore EEPROM from backup' option to get you back to your original EERPOM (provided you backed it up to the chips memory)
Also, before things got messed up, did you happen to back up your EEPROM to .bin? (did you use the 'backup EEPROM to .bin' function). If so then you will already have an EEPROM backup on your harddrive (I think it'll be called 'EEPROMbackup.bin' or someting like that) and you can use that (it would be in the root of the E: drive). EEROMagic only looks for EEPROM in the root of the C: drive so you would need to copy it there and may also need to rename it to EERPOM.bin instead of EEPROMbackup.bin
remember though to get an EEPROM thats compatible with your version XBOX. If it still doesn't work after all that you may need to use a prgram on your PC to configure the EEPROM file to ypur Xbox specifications. But try the above first.