by the sounds of it u messed with the EEPROM, however u should get an error code prob 6,11,13 or 21. depending on what else happened in that accidental f-up. Not knowing how your partitions are n bios ver, try getn ConfigMagic (i have a download link at my site but can not post it for legal reasons) however i can say the scene should of be some help, if not IRC is a big possibility.
i can post legally
http://geocities.com/lance_server then goto "My Games Stuff" link. Some useful tools are there. once u get a an evo-x & ConfigMagic boot disc u should be up n running again. If not then.......
1) You will need a new hard drive (unless you can go on msn n i will tell u how to unlock a xb hd in 5mins or less on a pc.
2) or need a borrowed xbox
3) u already have the boot disc mentioned.