Your cfg file looks good, assuming C:\opentelemac\metis-library\libmetis64b.lib exists already and has been compiled with the same compiler.
Try replacing xilib.exe by xilink.exe -lib in your config file (you will have to recompile with a -m "clean system"). This may get around your problem.
Also, do check if there is lib.exe in "C:\Program Files\Microsoft Visual Studio 8\VC\Bin" If you see missing files, you may have to re-install your fortran compiler integration with MS Visual Studio.
Hope this helps.
Sebastien.