Figured it out - it's not an Opera problem after all. It's a problem with the Web application I'm using. Sorry to cast aspersions on Opera!

Thanks for responding. I did set the Windows defaults and when I open the file from Windows Explorer, the viewer I want is used. However, Opera seems to have it's own preferences and utilizes Paint. In searching the Web I feel like I saw that in older versions of Opera you could change the programs associated with files but I'm not seeing any way of doing this in version 33. I think Opera should use the Windows defaults but...it's not.

I am using Opera 32 and I can't see anything in Preferences that allows me to establish what program is utilized for what file type. When I click on a TIFF file, Paint is used. However, I have another viewer that I want to use. I have that other viewer set as the default program in Windows. But it seem like Opera has its own set of preferences? Very frustrating! Any help would be appreciated, thanks.