Undefined File Extension
Undefined is associated with undefined file connection. As a solution you may install an antivirus software and scan your computer.
Generally, when a file is deleted from computer, or file is corrupted because of the viruses this warning occurs. It stands for undefined file connection.
As a solution, firstly you should install an antivirus software and scan your computer. If the warning comes from a software opening, it may search for the file which opened the one before. Open the software and read particular file and shut down. If Undefined error occurs at beginning, instead of making uninstall, the file which you deleted caused this. You should check the shortcuts which opens automatically at startup.
What needed to Open Undefined file extensions.
Scanner software may generate
Links about Undefined file extension