Compaq laptop shut down frequently

I also have a 5 years old Compaq Presario 2140CA laptop. I tried to
use System Recovery CDs to reinstll it completely to original
manufacturer standards but the problem is that it just shuts down in
the middle of the recovery or reinstalling process. Previously it just
shuts down if I play a video or heavy software for 30 minutes or used
it normally for a few hours.

Right now, as it just shut down many times while I tried to use the
Recovery CDs, nothing is on the computer, not even an operating
system.

I guess some piece of hardware, maybe fan?

The other problem the compaq laptop had is that its ethernet modem
does not work. It just stopped working, I tried all the methods and
called with DSL service company's support line and did all the things
they suggested. The computer did not talk with the DSL modem (from the
DSL company) when I type 192.168.0.1 or 192.168.1.1. All my other
computers connect perfectly to Internet through the same DSL modem.

Sorry I am not a tech person. Hope you understand and appreciate
helps.