Hi,
try to power your xbox with the exploitable game in the dvd drive. If it boots the game, you can try to install the game exploit again.
if this doesn't work anymore, you will need to fix the harddisk. If you have a backup of your xbox eeprom (eeprom.bin) it can be done fairly easy with the xboxhdm and kingroach ndure 3.1 package.
there is no need to use a bunch of four letter words in this forum. This wont help you any further.
Admid you messed up your xbox yourself, and don't blame it on microsoft or the guys who developped the modding tools.
If you don't have the eeprom.bin, your options are limited:
1. Temporary install a modchip to get that file.
2. Build an eeprom reader to get that file.
3. Do a hotswap. This can damage your harddisk, your xbox or your pc. You only need a set of Torx screwdrivers to open your xbox. Thats why a lot of people choose for this method.
regards.