Getting beeps when I boot up my system

Hello,

My MacBook Air 13" 2008 is having problems

When I press Power button my MacBook does not turn on, after 2 seconds I get 1 beep sound continuously.

Is my MacBook Air too hot? I tried recovery install with the (Hold Command R) Power on.

Sometimes the screen comes up with the Apple logo few minute after freezz.

Why is this happening? Please any ideas.

Thanks, Hamid