Custom Login dialog for WIX Toolset. Make sure you include a <UIRef Id="CustomUI_Login" /> in your Product.wxs file

LoginDlg.wxs

<?xml version="1.0" encoding="UTF-8"?>
<Wix xmlns="http://schemas.microsoft.com/wix/2006/wi">
  <Fragment>
    <UI Id="CustomUI_Login">
      <Dialog Id="LoginDlg" Title="!(loc.InstallDirDlg_Title)" Width="370" Height="270" NoMinimize="no">

        <Control Id="NameLabel" Type="Text" X="75" Y="113" Width="100" Height="15" TabSkip="no" Text="&amp;User Name:" />
        <Control Id="NameEdit" Type="Edit" X="75" Y="125" Width="220" Height="18" Property="LogonUser" Text="{80}" />
        <Control Id="PasswordLabel" Type="Text" X="75" Y="150" Width="100" Height="15" TabSkip="no" Text="&amp;Password:" />
        <Control Id="PasswordEdit" Type="Edit" X="75" Y="162" Width="220" Height="18" Property="PASSWORD" Password="yes" />
        
        <Control Id="InstallButton" Type="PushButton" Text="Login" Height="17" Width="56" X="130" Y="190">
          <Publish Event="NewDialog" Value="ProgressDlg"></Publish>
        </Control>

        <Control Id="CancelButton" Type="PushButton" X="190" Y="190" Width="56" Height="17" Cancel="yes" Text="!(loc.WixUICancel)">
          <Publish Event="SpawnDialog" Value="CancelDlg" >1</Publish>
        </Control>

        <Control Id="Description" Type="Text" X="25" Y="23" Width="280" Height="15" Transparent="yes" NoPrefix="yes">
          <Text>Click Login to finalise product installation</Text>
        </Control>

        <Control Id="Title" Type="Text" X="15" Y="6" Width="200" Height="15" Transparent="yes" NoPrefix="yes">
          <Text>{\WixUI_Font_Title}Log into system</Text>
        </Control>

        <Control Id="LoginHeaderText" Type="Text" X="35" Y="65" Width="300" Height="50" NoPrefix="yes">
          <Text>{\WixUI_Font_Bigger}Please enter your login username and password to continue:</Text>
        </Control>
        
        <Control Id="BannerBitmap" Type="Bitmap" X="0" Y="0" Width="370" Height="44" TabSkip="no" Text="!(loc.InstallDirDlgBannerBitmap)" />
        <Control Id="BannerLine" Type="Line" X="0" Y="44" Width="370" Height="0" />
        <Control Id="BottomLine" Type="Line" X="0" Y="234" Width="370" Height="0" />
      </Dialog>

    </UI>

    <InstallUISequence>
      <Show After="ProgressDlg" Dialog="LoginDlg">NOT Installed</Show>
    </InstallUISequence> 

  </Fragment>
</Wix>

Make sure you include a <UIRef Id="CustomUI_Login" /> in your Product.wxs file