You're not gonna like this....

http://www.xbox-hq.com/html/xbox-tut...boxerrorcodes1

1.Green/Red Flashing

Problem: The Xbox will restart twice, and then flash red and green. This is known as the FRAG and can be caused by many reasons. Typically when you receive this error you will not have any video. Possible reasons you may get this is a bad bios image, a bad bios chip, the Nvidia MCPX chip is damaged, broken/damaged traces or solder splashes on the mother board.

Fix: If you were doing any kind of soldering work (adding a Modchip or other type of mod) on or around your motherboard, make sure there are no solder splashes or that there are not solder bridges connecting any traces. If there are, desolder them. If you have not done any kind of modding to the unit, then its likely to be caused from a bad tsop image, or a bad chip. Try installing a Modchip to see if you can get the unit to boot. If the Xbox still gives a FRAG then it means another major component is bad and the motherboard needs to be replaced.
Sounds like you need to get a new Xbox.