Open the vCard .vcf file in Notepad and look for a line like this:

   BDAY:19600501

That's the birthday information for someone born May 1, 1960. If you don't
see something like that, it may be that Outlook 2000 just doesn't include
that information when it saves a vCard. (Outlook 2003 does.) You can type it
in yourself in Notepad, then save and send the file, but the boss' copy of
Outlook might not recognize it.

Alternatively, don't send a vCard. Send an actual Outlook item. Create a new
message in rich-text format and use the File | Insert command to insert the
contact. You may also need to double-click the underlined address in the
message and mark the boss' address for rich-text.