PKG_CONFIG_PATH variable

[millward <millward Ms UManitoba CA>]

Could someone tell me how to set the 
PKG_CONFIG_PATH environment variable?
I've upgraded rpm -Uvh glib2-2.0.4-1gtk.i386.rpm,
but when I do a:
 pkg-config glib-2.0 --modversion 
I get an error message:
 Package glib-2.0 was not found in the pkg-config 
search path. Perhaps you should add the directory 
containing 'glib-2.0.pc' to the PKG_CONFIG_PATH
environment variable. No package 'glib-2.0' found.

I have checked .bashrc and .bash_profile for both
my root and user account and neither has the
PKG_CONFIG_PATH listed.
glib-2.0.pc is in /usr/lib/pkgconfig
 This is what glib-2.0.pc looks like:

prefix=/usr
exec_prefix=/usr
libdir=/usr/lib
includedir=/usr/include

Name: GLib
Description: C Utility Library
Version: 1.2.10
Libs: -L${libdir} -lglib
Cflags: -I${includedir}/glib-1.2 -I${libdir}/glib/include

Nothing in it about version 2.0.4 or 2.0 at all.
So far, upgrading GTK has been very frustrating.
Any suggestions would be most welcome.