my computer is getting very hot very fast

Hi

I bought a macbook about six months ago and all was working fine. But within the last 2 weeks my mac gets very hot after just a 30 mins use. When i have a couple of applications, mainly itunes, skype and a computer game running, at the same time, the cooler goes nuts and gets very noisy because the mac is getting so hot. When iv been using the mac for 3-4 hours in a row the mac freezes and the rainbow colored symbol appears. The only option i have is to hit the power button and restart the mac.

My mac is on a stable surface(a normal working desk), so there air have no problem circle around. The games i play is between 2-5 years old so it shouldnt be a problem for this computer to run the games.

anyone who has a idea what the problem could be?

thanks for your time