Hi Sylvia and anyone else who is worried,

I write my e-mails on the Japanese version of Eudora. Any Microsoft
mail-reader detects that an incoming message from me was written on a
Japanese machine and automatically assumes therefore that it will be in
Japanese. It then scans your system and if it can't detect Japanese
character support, it reasonably asks you whether you want to download
Microsoft's own free Japanese character support plug-in. As I write in
English, you don't need this and should simply press 'cancel'. This is not
a virus.

Paul Callomon.