Error 1001. The specified service already exists. Existing service can't removed

The best solution I have found to "Error 1001. The specified service already exists" when installing/upgrading/repairing a Windows Service project is to modify the ProjectInstaller.Designer.cs.

Add the following line to the beginning of InitializeComponent() which will trigger an event before your current installer tries to install the service again. In this event we will uninstall the service if it already exists.

Be sure to add the following to the top of the cs file to implement the following namespaces...

using System.Collections.Generic;
using System.ServiceProcess;

Then use the following as show below in the example...

this.BeforeInstall += new
System.Configuration.Install.InstallEventHandler(ProjectInstaller_BeforeInstall);

Example:

private void InitializeComponent()
{

    this.BeforeInstall += new System.Configuration.Install.InstallEventHandler(ProjectInstaller_BeforeInstall);

    this.serviceProcessInstaller1 = new System.ServiceProcess.ServiceProcessInstaller();
    this.serviceInstaller1 = new System.ServiceProcess.ServiceInstaller();
    // 
    // serviceProcessInstaller1
    // 
    this.serviceProcessInstaller1.Account = System.ServiceProcess.ServiceAccount.LocalSystem;
    this.serviceProcessInstaller1.Password = null;
    this.serviceProcessInstaller1.Username = null;
    // 
    // serviceInstaller1
    // 
    this.serviceInstaller1.Description = "This is my service name description";
    this.serviceInstaller1.ServiceName = "MyServiceName";
    this.serviceInstaller1.StartType = System.ServiceProcess.ServiceStartMode.Automatic;
    // 
    // ProjectInstaller
    // 
    this.Installers.AddRange(new System.Configuration.Install.Installer[]{
            this.serviceProcessInstaller1,
            this.serviceInstaller1
        }
    );
}

The below code called by the event will then uninstall the service if it exists.

void ProjectInstaller_BeforeInstall(object sender, System.Configuration.Install.InstallEventArgs e)
{
    List<ServiceController> services = new List<ServiceController>(ServiceController.GetServices());

    foreach (ServiceController s in services)
    {
        if (s.ServiceName == this.serviceInstaller1.ServiceName)
        {
            ServiceInstaller ServiceInstallerObj = new ServiceInstaller();
            ServiceInstallerObj.Context = new System.Configuration.Install.InstallContext();
            ServiceInstallerObj.Context = Context;
            ServiceInstallerObj.ServiceName = "MyServiceName";
            ServiceInstallerObj.Uninstall(null);

            break;
        }
    }
}