Can I upgrade my Centos 4.1 system with the 4.2 ISO install disc?

If so, how do I do it?  It seams to want to do a full (i.e. format, wipe out old)
install over everything.  I do not want to lose my various configurations
(e.g. kppp, kde desktop settings, etc) that I have already set up under
4.1.