This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
Yes, you can write the data out in any format you want. Especially if you use OutputStreams instead of Writers. It allows you to write the data byte by byte. However, you must fully understand the format that you are writing and ensure that your application meets those specifications. A copy of the specification for Word 97 documents can be found here: http://www.wotsit.org/download.asp?f=word8