The "Open With" dialog box appears when you try to open a file with an unrecognized extension. If you double-click a file to open it, Windows must determine which program to use. It makes this determination based on the file name extension – the three characters after the period.

For example, a file named "Letter2Mom.TXT" is a text file. Windows recognizes the TXT extension, and starts the Notepad text editor program.

A file named "Letter2Mom.HUH" is not recognized. Double-clicking this file results in the "Open With" dialog box appearing.

How do I correct the error?

If the file is not recognized, choose a program to open the file or rename the file.

Select a program to open the file in the "Open With" window:

1.     If you know which program can open this file, click the program in the Open With         window. If it is not listed, click "Other…" to search for it.

2.     If you do NOT want every file with this extension ("HUH," in the above example) to be         opened with the program you select, click the checkbox to REMOVE the check mark.

3.     If you leave the check mark, Windows will continue to use the same program for all         files with the same extension. Type a description of the file type in the field above         the program list.

4.     Click "OK."

Change the file name extension:

1.     Right-click the file.

2.     Click "Rename."

3.     Use the arrow keys or mouse to place the cursor.

4.     Type an extension that Windows recognizes.

5.     Type "Enter." A message might appear warning that the file may become unusable. If         you are sure you are using an appropriate extension, click "Yes." You can always         rename the file again with its original extension.