File association, always open file with extension

I am using a Linksys remote video to capture movement in
a room on video. This is then sent by email to my
computer and I open the videos by clicking on the file,
which has an .asf extension (Linksys by default).

I use Winamp to open the file.

The problem is there may be as may as 15 to 20 emails to
open. When I click on the email I then click on the
*.asf file, which always prompts me twice to open the
file. In Xp under file associations on the advanced tab,
you could request "Always open files with this
extension". In Vista there is no Advanced tab.

Is it possible to force Vista to let Winamp open files
with this extension without being asked repeatedly to
open ?

Thanks

Sorry posted to wrong newsgroup.
Actually solved by running Outlook as administrator and
unchecking the prompt.