[vtkusers] vtkPNMReader Unknown file type

[raf.califano at libero.it]

Hi all,
I am a new user of vtk. i have installed vtk 5.2.0 and i work with vc++.
I would read a PGM image format but i get the follow error:
Unknown file type! is not a binary PGM or PPM!
The header file is 
P2
# created by 'xv balloons_bw.tif'
640 480
255
but vtkPNMReader can read only P5 and P6! (So I think)
Please help me.
Excuse me for my English.
Best Regards

Raffaele Califano