1. Если ActiveDirectory, то чем GPO не устраивает? -
Статья
2. Ну или так:
[reflection.assembly]::loadwithpartialname('System.Windows.Forms')
[reflection.assembly]::loadwithpartialname('System.Drawing')
$notify = new-object system.windows.forms.notifyicon
$notify.icon = [System.Drawing.SystemIcons]::Information
$notify.visible = $true
$notify.showballoontip(10,'WARNING','Automatically logoff after 1 hour of inactivity',[system.windows.forms.tooltipicon]::None)
3. Ну или совсем простое окно:
#creating object os WScript
$wshell = New-Object -ComObject Wscript.Shell -ErrorAction Stop
#invoking the POP method using object
$wshell.Popup("please wait message?",5,"Wait Until Scrip execution",48+4)