PlusService.exe appears to check if Plus! has been removed and then informs the user that it happened without their knowledge and redownloads Plus! for installation.
xml code:
<?xml version="1.0" encoding="utf-16"?>
<!-- Messenger Plus! 5 Interface Files -->
<Interfaces xmlns="urn:msgplus:interface" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="urn:msgplus:interface ../Schemas/PlusInterface.xsd" Name="Setup">
<GlobalColors>
<GlobalColor Id="title">
<BaseColor>
<Saturation>0.4</Saturation>
<Brightness>0.60</Brightness>
<Transparency>250</Transparency>
</BaseColor>
</GlobalColor>
<GlobalColor Id="ref">
<BaseColor>
<Saturation>0.4</Saturation>
<Brightness>0.60</Brightness>
<Transparency>220</Transparency>
</BaseColor>
</GlobalColor>
</GlobalColors>
<Window Id="PlusMissing" Version="1">
<Attributes>
<Caption>Reinstall - Messenger Plus!</Caption>
</Attributes>
<TitleBar>
<Title>
<Text>Warning</Text>
</Title>
</TitleBar>
<Position ClientWidth="296" ClientHeight="112"/>
<DialogTmpl>
<BottomBar Style="Default">
<RightControls>
<Control xsi:type="ButtonControl" Id="BtnDownload">
<Position Top="0" Width="130" Left="0"/>
<Attributes>
<IsDefault>true</IsDefault>
</Attributes>
<StandardLook Template="Blue"/>
<Caption>&Reinstall && Repair</Caption>
</Control>
<Control xsi:type="ButtonControl" Id="BtnCancel">
<Position Top="0" Width="50" Left="0"/>
<Caption>&Cancel</Caption>
</Control>
</RightControls>
</BottomBar>
</DialogTmpl>
<Elements>
<Element xsi:type="FigureElement" Id="FigRectInfo">
<Position Top="29" Left="9" Height="56" Width="279"/>
<Figure>
<RoundRect>
<Radius>4</Radius>
</RoundRect>
</Figure>
<Border>
<Color>
<GlobalColor>bg</GlobalColor>
</Color>
</Border>
<Fill>
<PlainColor>
<Red>255</Red>
<Green>255</Green>
<Blue>255</Blue>
<Alpha>120</Alpha>
</PlainColor>
</Fill>
</Element>
<Element xsi:type="ImageElement" Id="ImgUpdate">
<Position Top="34" Left="14"/>
<Image>
<Name>icon-update</Name>
</Image>
</Element>
</Elements>
<Controls>
<Control xsi:type="StaticControl" Id="LblTitle">
<Position Top="4" Width="278" Left="10" Height="12"/>
<Color>
<GlobalColor>title</GlobalColor>
</Color>
<Font>
<Bold>true</Bold>
<Size>8</Size>
</Font>
>>> <Caption>Important Note from the official Messenger Plus! software.</Caption><<<
</Control>
<Control xsi:type="StaticControl" Id="LblText1">
<Position Top="15" Width="277" Left="10"/>
>>> <Caption>Your Messenger Plus! is missing!</Caption><<<
</Control>
<Control xsi:type="StaticControl" Id="LblText2">
<Position Top="33" Width="241" Left="45" Height="30"/>
<Transparency>180</Transparency>
>>> <Caption>It seems like Messenger Plus! has been removed from your PC without your authorization.</Caption><<<
</Control>
<Control xsi:type="StaticControl" Id="LblText3">
<Position Top="63" Width="241" Left="45" Height="20"/>
<Transparency>180</Transparency>
>>> <Caption>Clicking on the button below will reinstall and repair Messenger Plus!.</Caption><<<
</Control>
</Controls>
</Window>
<Window Id="UpdateDownload" Version="2">
<Attributes>
<ShowInTaskbar>false</ShowInTaskbar>
</Attributes>
<TitleBar>
<AllowMinimize>false</AllowMinimize>
<Title>
<Prefix>Full</Prefix>
>>> <Text>Downloading Update</Text><<<
</Title>
</TitleBar>
<Position ClientWidth="220" ClientHeight="59"/>
<DialogTmpl>
<BottomBar Style="Default">
<RightControls>
<Control xsi:type="ButtonControl" Id="BtnCancel">
<Position Top="0" Width="50" Left="0"/>
<Caption>&Cancel</Caption>
</Control>
</RightControls>
</BottomBar>
</DialogTmpl>
<Controls>
<Control xsi:type="StaticControl" Id="LblTop">
<Position Top="4" Width="204" Left="7"/>
<Transparency>190</Transparency>
>>> <Caption>Please wait while the update is being downloaded...</Caption><<<
</Control>
<Control xsi:type="ProgressControl" Id="PrgDownload">
<Position Top="17" Width="206" Left="7"/>
</Control>
<Control xsi:type="StaticControl" Id="LblStatus">
<Position Top="34" Width="150" Left="7"/>
<Transparency>190</Transparency>
>>> <Caption>(update %1!d! of %2!d!)</Caption><<<
</Control>
</Controls>
</Window>
</Interfaces>