Send to Mail recipient problem

I run Win2K + Office 2000 on the network at work – along with Lotus Notes 5.0.7 as mail client.
On some of the PC’s the Send to Mail recipient inside the office applications does not fire of Notes – but instead Outlook or Outlook Express is started.
Notes is set up as E-mail program inside IE’s Tools / Alternatives on all the PC’s even those wiht this problem.

I can’t find anywhere else to configure which e-mail program should start from the Office apps. send to email recipient.

Anyone for a solution ?