how to install RHEL 3 in SATA HDD
 

i have core 2 duo 200 GB HDD 1GB ram

Here's a web page that you should put in your browser bookmarks if you are going to use RHEL 3. I imagine that the answer to your question is somewhere in here.

https://www.redhat.com/docs/manuals/...RHEL-3-Manual/

RHEL 3 is pretty obsolete---even RHEL 4 did not support SATA.

Do you have to use RHEL? If not, consider something like Fedora.
Also, look at CentOS (free clone of RHEL)

If you are just installing save yourself the headaches and go with RHEL/Centos5.2. The newer versions will support so much more hardware straight out of the box than earlier versions it is not funny.