Error installing plugin

[John Shane]

Hello list, I'm a new xfce4 user after trying Gnome, KDE, Ice and a few others.  Xfce4 definitely creates the desktop environment I've been looking for.  It's great, but now I've run into a problem trying to install plugins and I'm in a bit over my head. ;-) I could use some help interpreting the error message below. and a pointer where to look for the answer.  

I downloaded the plugin source tarballs from berlios.de and unpacked them.  I then changed to the directory with all the unpacked files and as root ran "./configure && make && make install" as per the instructions at the goodies site.  However, I get the following error:

<snip>
checking for bind_textdomain_codeset... (cached) yes
checking for locales directory... ${prefix}/share/locale
checking for pkg-config... no
*** The pkg-config script could not be found. Make sure it is
*** in your path, or set the PKG_CONFIG environment variable
*** to the full path to pkg-config.
*** Or see http://www.freedesktop.org/software/pkgconfig to get pkg-config.
configure: error: Library requirements (xfce4-panel-1.0 >= 3.99.2) not met; consider adjusting the PKG_CONFIG_PATH environment variable if your libraries are in a nonstandard prefix so pkg-config can find them.

I have a RH9 system. I installed Xfce4 using RPMs and am aware that the directories used are slightly different from the source defaults. I set my PKG_CONFIG_PATH variable using "export PKG_CONFIG_PATH=/usr/lib/pkgconfig"  When I check env PKG_CONFIG_PATH is pointing to the right directory with the xfce4 *.pc files.  I also went to the freedesktop site and downloaded the pkg-config tarball and tried to install it.  "Tried" is the operative word there.  I don't think I got it right though because I still can't get the plugins to work.

Here is what my /usr/lib/pkgconfig directory looks like:

[root at rdlaptop pkgconfig]# ls -l
total 64
-rw-r--r--    1 root     root          205 Jan  7 23:05 dbh-1.0.pc
-rw-r--r--    1 root     root          213 Jun 18  2002 fribidi.pc
-rw-r--r--    1 root     root          215 Feb  4  2003 gnome-mime-data-2.0.pc
-rwxr-xr-x    1 root     root          158 Feb  6  2003 gnome-python-2.0.pc
-rw-r--r--    1 root     root          156 Jan 25  2003 gtk-engines-2.pc
-rw-r--r--    1 root     root          170 Feb 20  2003 gtk-thinice-engine-2.pc
-rw-r--r--    1 root     root          275 Feb 25  2003 libmetacity-private.pc
-rw-r--r--    1 root     root          279 Feb 25  2003 libnautilus.pc
-rw-r--r--    1 root     root          261 Feb 25  2003 libpanelapplet-2.0.pc
-rw-r--r--    1 root     root          315 Jan  7 23:07 libxfce4mcs-client-1.0.pc
-rw-r--r--    1 root     root          318 Jan  7 23:07 libxfce4mcs-manager-1.0.pc
-rw-r--r--    1 root     root          247 Jan  7 23:06 libxfce4util-1.0.pc
-rw-r--r--    1 root     root          387 Jan  7 23:07 libxfcegui4-1.0.pc
-rw-r--r--    1 root     root          316 Jan  7 23:11 xfce4-panel-1.0.pc
-rw-r--r--    1 root     root          304 Jan  7 23:08 xfce-mcs-manager.pc
-rw-r--r--    1 root     root          238 Jan  7 23:14 xffm-1.0.pc

Thanks for any help you can give.  John