I'm no expert on this and I don't own a X Box, but it could be that you have cooked it. A friend of mine had the same thing happen. An X Box needs open space, as it heats up alot. Read the instructions, it goes into detail regarding this

Your Xbox was crying out for rescuing but you kept ignoring it (normal bootup sequence should be less) I suggest you format the retail HDD and then rebuild it. I successfully resurrected my un-chipped box with more or less the same problem (DEAD?!) I'm not promising you anything but if I were you I'd be ready to try anything! ---------------------------------------------------------------------------------------------------------------------- Rescuing an Xbox Retail HDD; "Error 21"; "Error 7"; "NULL BOOT"; "DEAD HDD" ---------------------------------------------------------------------------------------------------------------------- This relates to an un-modded Xbox with a dead HDD or which gives either "Error 21" or "Error 7". Note: You will lose all gamesaves and other stuff on the dead HDD as this procedure requires formatting. You need an extra Xbox with a modchip and "Slayer's Auto-Installer DVD" First, Open the top covers of both the Xbox units. Go to the modded Xbox and dismantle the HDD tray.. Remove the HDD fastening screws that are on the sides of the HDD tray... Do the same with the other Xbox.. Now place both the HDDs on the Xboxs' realtively close to each other.. If they are still not close enough.. Use a Y connector or an extension to the power connector of the HDD on the unmodded Xbox.. with this, you should be able to place the HDD on the DVD drive.. Place both the Xbox HDDs close to each other Now, Attach the modded Xbox to AV2 on your TV and the troubled or dead Xbox to AV1. Switch to Av2, Power on the modded Xbox, and place the Slayers Auto-Installer DVD into the dvd Drive. Wait for this to load.. Now switch to AV1, Power on the Xbox with the dead HDD, Now when the big "X" comes on the screen remove the IDE cable from the HDD.. REMEMBER to leave the power connected to the dead HDD, If you have done this correctly.. Your dead HDD is now unlocked and is on its way to being restored. ___Remember to take out the IDE cable from the HDD before the error msg appears on screen____ Now switch back to AV2 on your TV, (this is the modded Xbox) Take out the IDE cable from the HDD on the Modded Xbox and connect it to the dead HDD.. _make sure you havent disconnected the power supply to the dead HDD_ Otherwise, start over. Take your controller and goto option to "restore/rebuild retail HDD" on the menu of Slayers Auto-Installer. Click "Yes" to all the prompts and Slayers should take care of the rest. After the procedure. Remove the IDE cable from the now restored HDD and attach it back to the original IDE cable of the retail unmodded box. Power off. Switch to AV1, and power on the unmodded Xbox. If you have correctly HOTswapped.. the HDD should be rescued & restored Power off both Xbox units, and replace the IDE cable to the modded Xbox HDD, If you have used a Y connector or a power extension remove it, and attach the power supply directly to the HDD. Fasten the screws on the HDD trays as well, Now put the covers back and fasten all the 6 screws at the bottom of both Xbox units. Youre good to go, Dude. domrosa at gmail dot com