PDN file cannot be read in Windows 7

I installed windows 7 and in Paint.NET I do photo retouching but when I finished I can not read the file of PDN Paint.NET. Please help.

Paint.NET is included in Windows 7? Are you sure?

Windows 7 is not over I think, in a beta test ... You must also be able to save in jpeg in your program normally;)

I'm guessing you added the ".PDN" extension yourself in Paint.NET while the "Save file as type" box was set on PNG. Adding periods to your file names messes them up. Don't do it. Just let Paint.NET itself do the extension work. And leave periods out.