char "_" can not insert in filenames

[Andreas Bauer]

Hello,

I can not insert char "_" in the filenames, which I want to generate in the 
homedrive of my Win XP samba users.
If I want to do this on my xp clients, an example of special characters, 
additional characters, is opened. But I think that char "_"
is not inherent to the list of special characters, which are  forbidden to 
insert into filenames?
I have tried: unix charset = utf-8, dos charset = 850, client code page = 
, not successfully.

Best regards
Andreas