i would like to know how to cold boot if someone could tell me

Stick game in....turn off...turn back on.

thought so

so if i coldboot i can play xbox live?

that depends on how your xbox is modded, if you have a softmod then yes coldbooting will let you play on live. if you have a modchip then you have to disable the chip. there might be a switch on it depending on how new it is or you might just have to turn the xbox on with a certain button or hold in the power button for a few seconds or something, tell us how your modded