When RadEditor with Bootstrap skin is inserted in the ContentTemplate of RadWindow, the tools look incorrect.

A temporary solution is to override  some CSS rules with more proper values:

<style>
    .RadWindow .RadEditor .Bootstrap.reToolbarWrapper .reToolbar .reToolLastItem .reTool {
         border-right-width: 0;
    }

    .RadWindow .Bootstrap.RadEditor.reWrapper .reSplitButton.reTool {
        width: 42px;
    }

    .RadWindow .Bootstrap.RadEditor.reWrapper .Bootstrap.reToolbarWrapper .reToolbar li {
        border-right-width: 1px;
        border-left-width: 0;
    }

    .RadWindow .Bootstrap.RadEditor.reWrapper .Bootstrap.reToolbarWrapper .reToolbar li.reToolFirstItem {
        border-left-width: 1px;
    }

    .RadWindow .Bootstrap.RadEditor.reWrapper .Bootstrap.reToolbarWrapper .reToolbar .reSeparator + li {
        border-width: 1px;
    }
</style>

<telerik:RadWindow runat="server" Width="1200px" Height="600px" VisibleOnPageLoad="true">
    <ContentTemplate>
        <telerik:RadEditor runat="server" Skin="Bootstrap">
        </telerik:RadEditor>
    </ContentTemplate>
</telerik:RadWindow>