Security warning message when clicking a hyperlink: "files might harm your computer"

Problem

You're giving a presentation using your own computer and every time you click a hyperlink, PowerPoint pops up an annoying warning about how your linked file might contain a virus. Something like this:

Opening "path/filename".
Hyperlinks can be harmful to your computer and data. 
To protect your computer, click only those hyperlinks from trusted sources. 
Do you want to continue?

They're your own files. If you're not a "trusted source", then who is?

The least of your worries is giving yourself a virus. If the files were infected, you already HAVE a virus. At this point, all you want is to be able to deliver a professional-looking presentation, free from gratuitous nattering like this.

The suggestions below may or may not work, or may work for some types of links but not all. Microsoft has gone WAY overboard with its attempts to protect us.

Possible Solution

See this if you're using Office 2007 or 2010.

If you're comfortable editing the registry ...

Note: If the following makes no sense to you, it might be best to leave the registry alone. See the FixIt links in the pages linked to above for alternate solutions.

Quit PowerPoint if it's running.

In Registry Editor, locate this subkey:

• For Office 2007: HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Common
• For Office 2010: HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Common
• For Office 2013: HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Common
• For Office 2016: HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common

Beneath Common, locate the Security subkey. If there isn't a Security subkey, create it.

Beneath Security, add a new DWORD value named DisableHyperlinkWarning and set its value to 1

Close the registry editor, start PowerPoint again and test.

Note: You can change this value back to 0 to re-enable hyperlink warnings. You may want to do this except when presenting so you know how your files will behave on other computers where hyperlink warnings are active.

Earlier PowerPoint versions

If you haven't moved to 2007 yet, no problem, PowerPoint MVP Chirag Dalal has you covered. He's created a small program that makes the required registry changes for you (and another that changes them back). Get them here

Remember: The registry change only affects your computer, not anyone else's. If you need to distribute presentations to others, you'll want to turn the warning back on while testing your presentation so you know what'll happen when other people view your work.

Keep in mind also that this registry change won't affect the PowerPoint 2003 viewer, just PowerPoint 2003 itself. The viewer will still issue warning messages when you click hyperlinks.

A visitor to the PowerPoint Newsgroup (thank you, Ramin!) suggested linking to a web page and letting the web page contain the links to the files that trigger the warning messages in PowerPoint.

Links to TIFF and MDI files behave differently

When opening linked TIFF images or Microsoft Document Imaging (MDI) files, you may see this slightly different message:

Opening path/filename.
Some files can contain viruses or otherwise be harmful to your computer. 
It is important to be certain that this file is from a trustworthy source. 
Would you like to open this file?

Microsoft has this to say:

You receive this warning message even when you have already implemented the registry key that this article describes. This warning message comes from the HLINK.dll file when link navigation is handled. You can differentiate the 2007 Office or 2010 Office hyperlink warning message from the HLINK warning message by looking for quotation marks around the file path in the warning message. The 2007 Office or Office 2010 message contains quotation marks. The HLINK message does not contain quotation marks. 2007 Office and Office 2010 try to determine whether the file type itself is unsafe by checking the extension, the progid, the classid, and the MIME type of the document.

This seems to be a lot of bafflegab that boils down to "Learn to live with it because we're not going to fix it."

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