How to associate Notepad to open files with no extension
When you double click a file containing no extension, the Open With dialog opens. In the Open With dialog box, you can click the program where you want the file to open, or click Browse to locate the program that you want.
However, the Open With dialog may not allow a permanent association for files with no extension, as the Always use the selected program to open this kind of file check box may be grayed out. This article tells you how to associate Notepad to open files with no extension.
The association for file names with no file extension can be set under the following registry key:
To associate Notepad to open files with no extension, use the following REG file. Copy the contents below to Notepad, and save the file with a .REG extension, say, noname.reg. Right-click the REG file and then choose Merge.
Windows Registry Editor Version 5.00