Yes. GnattProject has the ability to open and work with files created in Microsoft Project. However, to do this, you need to activate this option when you install the product. If you didn't make this available, you won't be able to work with files from Microsoft Project. Visit the application's review page from Software Informer in order to obtain a download link for the latest version. After you downloaded the installer package, open it, click Next on the first screen, on the second one make sure that you read carefully the License Agreement. When you finished reading, click the I Agree button. This will allow you to advance to the next screen. On this one, make sure that you have the last option checked (Open Microsoft Project files with GnattProject). On the last screen of the installer, you need to select a destination where you want to install the product and click the Install button. By following the steps provided above, you should be able to open your files in GnattProject.
