Assuming the file is already on your system, right click it and choose Open With, then navigate to firefox.exe in C:\Program Files\Mozilla Firefox.

From within Firefox use File > Open File...

If you want to do it the way the-edmeister suggested, you have to reconfigure the layout temporarily because in the new style, Firefox 4.0 doesn't have a "File" menu.

So what you have to do is this.

Right click a blank part of the Tab Bar and then click "Menu Bar" at the top. This will reinstate the text links, but remove the orange Firefox button from the layout. You can now click "File", then "Open File" and navigate to the location where the file resides like he suggests.

After that, repeat the same steps to remove the text links and reinstate the orange Firefox button and corresponding layout.

Sounds reasonable, and in my Program Files there is a firefox executable icon, BUT no firefox.exe

I'm running Windows Vista

Dave C

Sounds reasonable, and in my Program Files there is a firefox executable icon, BUT no firefox.exe

I'm running Windows Vista

Dave C

You probably have Vista configured not to show file extensions that's why.

So open Windows Explorer, then right click your C:\ drive and go to Tools, then Folder Options.

Then click the View tab and checkmark the radio button called "Show hidden files & folders". Then remove the checkmark from "Hide file extensions for known file types".

Apply/OK and then navigate to Mozilla Firefox in Program Files again.