reading Japanese e-mail in Outlook97

Hi. I'm using US-english Win98 and Outlook97. Sometimes I get Japanese emails from a Japanese friend. When I send a reply in english (with the original message attached), the original message in Japanese will turn out to be symbols on the receipientscreen. The same thing happens if I forward the mail and add messages.
Is there a add-on for Outlook or Windows98 that I can download, or must I change my Office97 to the International language version?
Thanks for all help.