[CentOS] Regd: Clarification on Linux Upgrade

Dear All,

    Currently i have using CentOS4.4 and Kernel Version is 2.6.9-42.EL.
    I want to upgrade my Linux to Stable Version of Linux (CentOS4.7)
   
    Clarification required about Linux upgrade is
    1. How do i upgrade my Linux and is their any document is available
    2. Where can i download the upgrade Linux iso
    3. Whether i can upgrade my Linux PC without any configuration data loss
        Example : http configuration, xinetd configuration, etc...

   Linux Degrade is possible or not
   Please can any help me
   Thanks in Advance.

Regards
-S.Balaji