Welcome to the forums ...
If your OS on your BES is indicating that it cannot install the patch because it isn't appropriate for the version of software installed, then it can't be installed.
You could use regsvr32
to unregister the mapi32.dll, copy it over from the Exchange server, overwrite the dll, and then re-register it on your BES.
More importantly though ... were you able to apply this patch to Exchange and not BES?
Even more importantly ... time to upgrade; Exchange 2000 is past its time.