Red Hat Enterprise Linux 4 was made available on February 15, 2005. Full support for the product, including hardware updates, will last for the duration of February 15, 2005 to August 31,2007. Deployment support will be available from September 1, 2007 to February 29, 2008.
Maintenance Support: Mar 1, 2008 to Feb 29, 2012
Maintenance support will be available from March 1, 2008 to February 29 31, 2012 as per Red Hat Enterprise Linux 4's 7 year product support life cycle.
Updated ISO images are available on Red Hat Network (RHN).
Information on Red Hat Enterprise Linux product lifecycles can be found on: http://www.redhat.com/security/updates/