Hyperlink to TIF File - Not Trusted
 

I have a table with hyperlinks to .TIF images. Whenever I activate the link,
I get a message:

Opening <myfilename
Some files can contain viruses or otherwise be harmful....
Would you like to open this file?

How do I avoid getting this time-wasting message?

I have added the directory containing these images to "Trusted Locations" -
Makes no difference.

I have tried enabling all External Content, Macros, etc. - Makes no
difference.

Any ideas?

Sean