I have a older emachine that my son was trying to install a comcast high speed internet cd onto .But shortly after the computer began shutting off by itself and eventually wouldnt reboot. We tried to to use the recovery disc but the computer keeps shutting down Help anybody

By shutting down, do you mean it powers off or actually does a shutdown? If it drops power and it's an older eMachine, I would suspect defective capacitors on the system board or in the power supply.

See here for some info: Capacitor plague - Wikipedia, the free encyclopedia

Check that first, then post back with results please.