Hello: I was running a racing game called Grid and my cpu is around 70-90 all the time, and, as usually, when the usage go up like that, my cpu/fan produces much higher noise. I am really really worried it is going to kill my computer. Is it possible my computer will have much shorter life if I get that kid of high usage a lot? I have XFX Geforce 8800 GT and Pentium D 2.8GZ. Thanks

I'm surprised it wasn't 100% to be honest. Usually games use as much processor time that they can get their hands on, which usually means a constant 100% usage while playing.
And to answer your question, as long as your temps are not high, no, you'll be fine.