Some antivirus softwares detect falsely viruses in our game client.
There are no viruses in our mu online client!
You have to stop your antivirus software and extract the game again to fix this error, or need add the game client in your antivirus list of exclusions.
Windows Defender deletes Select server from MuWar.net Launcher 2.exe. You need to stop it or add exclusions.
and select Update & Security > Windows Defender.
Under Exclusions, select Add an exclusion
Select Add button, navigate to the file, folder, or process, and then select Exclude this file. (We recommend selecting the entire folder)
Online help - Click here
Settings > Antivirus > Exclusions > Select Client folder
and click Add > OK
Options > Advanced Settings > Exeptions > Add exception
> Application or file > Browser (select main.exe, MuWar.net Launcher.exe and Updater.exe from Client folder) > OK
Microsoft Security Essentials
Settings > Excluded files and locations > Browse > Select client folder
(Example C:/Games/Mu) > Add > Save Changes
After you ready with add client folder to the exceptions of your antivirus, extract again the game client in the same directory.