error when when making package tcltk from source (R.0.1)

Dear R-Helpers,

I am working with Windows XP.
I am trying to build R 2.0.1 from source (R-2.0.1.tar.gz downloaded from 
CRAN).
I read the R Installation and Administration manual and the 
README.packages file as well (probably tot carefully enough !).

I installed the recommended tools and software including TCL/TK software 
(from archive ActiveTcl8.4.9.0.121397-win32-ix86.exe). I modified the 
PATH system variable and created new user variables:

TCLTK_CPPFLAGS=C:\tcl\include
TCLTK_LIBS=C:\tcl\lib

I meet the following error when building R:

CD C:\R-2.0.1\src\gnuwin32
make all bitmapdll recommended vignettes

[snip]

---------- Making package tcltk ------------
   adding build stamp to DESCRIPTION
   installing NAMESPACE file and metadata
   running src/Makefile.win ...
gcc  -IC:/R-2.0.1/include -Wall -O2 -I "C:/R-2.0.1/Tcl"/include -DWin32 
  -c init.c -o init.o
tcltk.h:3:17 tcl.h: No such file or directory
tcltk.h:4:16 tk.h: No such file or directory
make[5]: *** [init.o] Error 1
make[4]: *** [srcDynlib] Error 2
make[3]: *** [all] Error 2
make[2]: *** [pkg-tcltk] Error 2
make[1]: *** [rpackage] Error 1
make: *** [all] Error 2

I checked in the Tcl installation and tcl.h and tk.h are actually in the 
tcl\include directory.

What did I do wrong, and how to fix it ?

Thanks and best regards,

Renaud

Dr Renaud Lancelot, v?t?rinaire
C/0 Ambassade de France - SCAC
BP 834 Antananarivo 101 - Madagascar

e-mail: renaud.lancelot at cirad.fr
tel.:   +261 32 40 165 53 (cell)
         +261 20 22 665 36 ext. 225 (work)
         +261 20 22 494 37 (home)