strange behaviorof replace-regexp on win xp

[renato . pontefice]

Hi,
I'm using the replace-regexp on win XP.
I need to replace some "tab" with null char.

I do:
--replace-regexp
---\\tab (in when it ask me wich char to replace)
----RETURN (to insert nothing in the replace)

emacs find about 96 replacement.

Then, I open the file with MS word, and I find that emacs, replace the tab, 
with space.
I want that it replace with null char, not space.

Can it be a win prob.?

TIA

Renato