We have an Intranet website, and a WPF windows executable installed on every workstation.
I have links to UNC folders/files inside my intranet portal and I've found that the clients need to have the local domain name "mycompany.local" added in their "Trusted Sites". I have also found this only works in IE (verified not working in FireFox and Safari).
Use the file:/// prefix.
Like so:
<a href="file:///C:/Windows/notepad.exe">asd</a>
I'm not sure if you'll be able to get past the security dialog though (open, save, cancel).
If you know the path for the file and it's the same on every machine, you can link to the local path:
<a href="C:\Windows\prog.exe">Click Here</a>
We did this at a previous company on our intranet. Worked, no problem.
If your users really use only IE you can use this snippet:
<script type="text/javascript">
function runNotepad() {
var Shell = new ActiveXObject("WScript.Shell");
Shell.Run("%WINDIR%\\notepad.exe");
}
</script>
<a href="#" onclick="runNotepad(); return false;">Run Notepad</a>
However, with any sensible security settings this leads to an awful lot of warnings (and rightfully so!).