Opening .tif attachments

[Teo]

Hi,
I think this should be pretty easy but i am having problems opening a .tif
file on a clients computer. Whenever a .tif comes as an attachment it will
not open. I want to change outlooks default attachment opening program fo
these files, how would i do this? For instance, in my email .tif files open
in 'microsoft office document imaging' but it could also open in 'fax viewer'
- 'office picture manager' and my user has these programs so i should just
need to redirect where it's resolving these files right?

Thanks,
Matt