|Files that start with a ~ (tilde) are typically temp files created by the application when a file is opened.|
In a perfect world, once the original file is saved/closed "normally" (as opposed to a crash or force-quitting via the Task Manager) the application is supposed do a little clean up and delete the temp files.
MS Office is notorious for not always cleaning up after itself and leaving those ~$ab.xyz files hanging around.
The original files should still exist, so there really is no need to try and open the temp files. Just delete them (Disclaimer: at your own risk).