>>Something like:
>>

>><ScrollViewer HorizontalScrollBarVisibilitty="Auto" VerticalScrollBarVisibility="Auto">
>>    <TabControl>
>>        <TabItem>
>>            <Grid>
>>                <Grid.ColumnDefinitions>
>>                    <ColumnDefinition Width="300"/>
>>                    <ColumnDefinition/>
>>                </Grid.ColumnDefinitions>
>>                <StackPanel>
>>                        <!-- Main Content, allow horizontal scrolling, don´t allow vertical scrolling-->
>>                </Stackpanel>
>>                <StackPanel Grid.Column="1">  // Allow Vertical Scrolling
>>                     <Expander>
>>                            <!-- Description 1 -->
>>                     </Expander>                     
>>                     <Expander>
>>                            <!-- Description 2 -->
>>                     </Expander>                     
>>                     <Expander>
>>                            <!-- Description 3 -->
>>                     </Expander>                     
>>                </StackPanel>
>>            </Grid>
>>        </TabItem>
>>        ...
>>    </TabControl>
>></ScrollViewer>
>>

>
>Look back at Viv's answer, that she wrote for you.
>
>What I can't figure out is why you are put a TabControl inside of a ScrollViewer. If you do that
>your tabs are going to scroll out of site which is generally not what is wanted in most designs.
>
>You want the ScrollViewer to be inside the TabControl and in this
>case you want two of them, one for the left side and one the right.
>
>Again look at Viv's code what she did should work for what you are describing.

Viv is he, not she.