There is built-in support for Windows 7 ISO Image. You can simply double-click an ISO image file and burn to a blank CD/DVD using built-in Windows 7 Disc Image burner application. But this gets broken when you install 3rd party program like WinRAR which supports opening ISO files as an archive. Now, when you double-click an ISO image file in Windows 7, you will not see the file opening with Windows 7 Disc Image burner. This you can easily restore by following the below tutorial.
How to Restore Windows 7 ISO image association to its default in Windows 7?
1. Right-click on any ISO image file and choose Open with → Choose default program as shown.
2. In the Open with window, select Windows Disc Image Burner from the list of programs. Then select the checkbox labelled Always use the selected program to open this kind of file as shown.
3. Click on the OK button to save the settings.
Windows 7 ISO image association restored!
After these changes in the settings, you should be able to restore the Windows 7 ISO image associations back to Windows Disk Image Burner app. The change in settings is immediate and you can start using the app, right away.