i'd try the method that 'mammuk' told... but the wav file is
affected by the effects... it cannot come out with the original
sound. can anyone teach me, how to overcome this problem? i want
to follow the song while i'm playing my guitar...

--- mumufuk comments ---
Man! why not to read the text at http://GuitarFX.Net before ask?
Clean guitar signal goes to the top fx-slot, then proceessed
by effects and outputed from the bottom fx-slot.
If you select "Playback" in the top fx-slot you will mix
wav file with clean guitar sound and process both!
So, place "Playback" in the bottom fx-slot, in this case
you mix processed guitar with non-processed wav file.