MS checks either HD sizes, or HD serial numbers now when you connect to live...i woudl DEFINAZTELY put back your old HD when going on live..ive heard of ALOT of people being banned with upgraded HD's with their modchips off...i remove my modchip just in case, i heard with 1.6 xboxes they send signals to the LPC to check for chips....i dont know if this is true, but i dont wanna risk it...it takes me about a minute to unplug my chip and put in my old HD