Well it seems Microsoft is taking steps to stop the modifying of there XBox`s and changes there hardware so the modchips dont work.
The new Xbox announced earlier by Team X-ecuter have now been confirmed by BOSSGP on the xboxhacker.net forums :
"after modding many many xboxes I want to confirm it's true there is a new version that came out during 8/2002
different things: re done mainboard, no fan on the nvidia video chip, small chip missing behind the onboard bios.
different connection for the control leads inside.small board is now missing that the control leads plugged into.NEW DVD ROM USED PHILLIPS BRAND, not as loud as the Thompson but still whats the point without a mod chip.
all mod chips I tried wont work. I will put some pics here tomorrow.with the new bios number as well ! !
If you fit the evox mod chip the machine wont power up, it's just keeps flashing, on/off no screen, no nothing.
Hope this is'nt a major setback in the mod chip world. "
Sony had done this before to with changing the motherboard and harware in there playstations but failed because the modchips where redisigned. You can read the full discussion on the new XBox Here in the XBOX hacker forum.
If you got an Xbox that was built after
08/2002 then you might not be able to use any modchip. They have made some significant changes on the inside of the box.