Word 98 formats

[Dark Servant]

Hello could someone please tell me how to send a Word 98 file in doc 
format. I need to send it to my Uni Lecturer who says I've sent him the 
files in dat format. Is this the translation in the Email or is it in 
the in the actual Word application. I'm kind of in a hurry with this 
one so quick responses would be greatly apreciated.
Running Mail in OS X.1.3 and Microsoft Word 98.

Ruben A. Franke