wrap your 360 in towels so all the ports are covered. than turn on the system for 30 minutes. after that let it cool down for 30 minutes. DONT TURN IT ON BEFORE THAN. after the time expires turn on you system. look up "360 towel trick" on youtube
i got Rrod during the peak of my Cod4 gaming, and did this. it worked for about a week and i just repeated this process with 100% succesion rate. i eventually sent in my xbox after i cooled of on the cod4. good luck!!
Btw... ALL xbox 360s have a 3 year warranty after date of manufacture but only for RRod.