Help! New user having problems compiling GTK, complaining of old GLIB

[resonant evil <air lightz gmail com>]

Hi all..  I am running Debian-STABLE right now, and manually
compiled the Cairo, Pango, ATK, and GLIB 2.8.5 sources and did a
make/make install on them all no problem, but now when I run a
./configure in the GTK directory, I'm getting this error:

checking for pkg-config... /usr/bin/pkg-config
checking for GLIB - version >= 2.7.1...
*** 'pkg-config --modversion glib-2.0' returned 2.8.5, but GLIB (2.6.4)
*** was found! If pkg-config was correct, then it is best
*** to remove the old version of GLib. You may also be able to fix the error
*** by modifying your LD_LIBRARY_PATH enviroment variable, or by editing
*** /etc/ld.so.conf. Make sure you have run ldconfig if that is
*** required on your system.
*** If pkg-config was wrong, set the environment variable PKG_CONFIG_PATH
*** to point to the correct configuration files
no
configure: error:
*** GLIB 2.7.1 or better is required. The latest version of
*** GLIB is always available from ftp://ftp.gtk.org/pub/gtk/.
airfoil:/home/duckdown/applications/gtk+-2.8.9#
It 
I am truly a new user trying to learn the ropes, but I have no clue how
to go about either A> Removing my old GLIB installation or B>
Designating it to the right installation

I am not even sure which version is installed where :S

If I try and unmark the glib-dev-2.0 or glib-2.0 from synaptic, it's
going to wipe out a whole ton of applications with it supposedly, so I
decided against it

The INSTALL file in the GLIB package tells me to to a "rm -fr
/install-prefix/include/glib.h and rm -fr
/install-prefix/include/gmodule.h", and upon further searching, it
would appear the 2 installations on my system are in /usr/include and
/usr/local/include (well, I'm assuming at least because it found those
files in both of those locations.)  I haven't a clue though which
one contains my GLIB-2.8.5 instead of the old one that configure is
complaining about.

I would appreciate any help or steps towards fixing this problem very
much, and I look forward to some help hopefully :(  Things like
this make Linux very discouraging for the new user :(

Thanks all.