Clicking a URL link in Office documents also launches another app.

When clicking a URL link in an Office document (e.g. Outlook mail item) the
browser launches with the correct content BUT ALSO another application
launches, specifically an installer for "Winter Dream Screensaver".

This symptom only seems to happen from within Office applications.

Using a command prompt with the same arguments is OK. Using a link in other
applications is OK.

Tried removing the screensaver and its setup program to no avail. Run at
least 3 anti-spyware applications.