I just recently tried installing CentOS on a old Toshiba laptop (Model: M45-S269) which has a DVD-RW drive but functions only as a CD drive. So the easiest option for me to install CentOS was through the Internet.
Here is what I did:
1) Depending on your PCs processor architecture download the CentOS netinstall.iso file from
CentOS 5.4 ISOs
2) I followed the steps described in the following URL CentOS NetInstall 5.3 written by Chris Gountanis