add this into your Buffs file then go to your file and at the bottom of your Buffs.xml where it says <DrawTemplate>WDT_Rounded</DrawTemplate> change to <DrawTemplate>WDT_Buffs</DrawTemplate>
Code:
<WindowDrawTemplate item="WDT_Buffs">
<Background>Buff.tga</Background>
<VSBTemplate>
<UpButton>
<Normal>A_VSBUpNormal</Normal>
<Pressed>A_VSBUpPressed</Pressed>
<Flyby>A_VSBUpFlyby</Flyby>
<Disabled>A_VSBUpDisabled</Disabled>
<PressedFlyby>A_VSBUpPressedFlyby</PressedFlyby>
</UpButton>
<DownButton>
<Normal>A_VSBDownNormal</Normal>
<Pressed>A_VSBDownPressed</Pressed>
<Flyby>A_VSBDownFlyby</Flyby>
<Disabled>A_VSBDownDisabled</Disabled>
<PressedFlyby>A_VSBDownPressedFlyby</PressedFlyby>
</DownButton>
<Thumb>
<Top>A_VSBThumbTop</Top>
<Bottom>A_VSBThumbBottom</Bottom>
<Middle>A_VSBThumbMiddle</Middle>
<OverlapLeft>0</OverlapLeft>
<OverlapTop>0</OverlapTop>
<OverlapRight>0</OverlapRight>
<OverlapBottom>0</OverlapBottom>
</Thumb>
<MiddleTextureInfo>scrollbar_gutter.tga</MiddleTextureInfo>
<MiddleTint>
<Alpha>255</Alpha>
<R>128</R>
<G>128</G>
<B>128</B>
</MiddleTint>
</VSBTemplate>
<HSBTemplate>
<UpButton>
<Normal>A_HSBLeftNormal</Normal>
<Pressed>A_HSBLeftPressed</Pressed>
<Flyby>A_HSBLeftFlyby</Flyby>
<Disabled>A_HSBLeftDisabled</Disabled>
<PressedFlyby>A_HSBLeftPressedFlyby</PressedFlyby>
</UpButton>
<DownButton>
<Normal>A_HSBRightNormal</Normal>
<Pressed>A_HSBRightPressed</Pressed>
<Flyby>A_HSBRightFlyby</Flyby>
<Disabled>A_HSBRightDisabled</Disabled>
<PressedFlyby>A_HSBRightPressedFlyby</PressedFlyby>
</DownButton>
<Thumb>
<Right>A_HSBThumbRight</Right>
<Left>A_HSBThumbLeft</Left>
<Middle>A_HSBThumbMiddle</Middle>
<OverlapLeft>0</OverlapLeft>
<OverlapTop>0</OverlapTop>
<OverlapRight>0</OverlapRight>
<OverlapBottom>0</OverlapBottom>
</Thumb>
<MiddleTextureInfo>scrollbar_Hgutter.tga</MiddleTextureInfo>
<MiddleTint>
<Alpha>255</Alpha>
<R>128</R>
<G>128</G>
<B>128</B>
</MiddleTint>
</HSBTemplate>
<CloseBox>
<Normal>A_CloseBtnNormal</Normal>
<Pressed>A_CloseBtnPressed</Pressed>
<Flyby>A_CloseBtnFlyby</Flyby>
<Disabled>A_CloseBtnDisabled</Disabled>
<PressedFlyby>A_CloseBtnPressedFlyby</PressedFlyby>
</CloseBox>
<QMarkBox>
<Normal>A_QMarkBtnNormal</Normal>
<Pressed>A_QMarkBtnPressed</Pressed>
<Flyby>A_QMarkBtnFlyby</Flyby>
<Disabled>A_QMarkBtnDisabled</Disabled>
<PressedFlyby>A_QMarkBtnPressedFlyby</PressedFlyby>
</QMarkBox>
<MinimizeBox>
<Normal>A_MinimizeBtnNormal</Normal>
<Pressed>A_MinimizeBtnPressed</Pressed>
<Flyby>A_MinimizeBtnFlyby</Flyby>
<Disabled>A_MinimizeBtnDisabled</Disabled>
<PressedFlyby>A_MinimizeBtnPressedFlyby</PressedFlyby>
</MinimizeBox>
<MaximizeBox>
<Normal>A_MaximizeBtnNormal</Normal>
<Pressed>A_MaximizeBtnPressed</Pressed>
<Flyby>A_MaximizeBtnFlyby</Flyby>
<Disabled>A_MaximizeBtnDisabled</Disabled>
<PressedFlyby>A_MaximizeBtnPressedFlyby</PressedFlyby>
</MaximizeBox>
<TileBox>
<Normal>A_TileBtnNormal</Normal>
<Pressed>A_TileBtnPressed</Pressed>
<Flyby>A_TileBtnFlyby</Flyby>
<Disabled>A_TileBtnDisabled</Disabled>
<PressedFlyby>A_TileBtnPressedFlyby</PressedFlyby>
</TileBox>
<Border>
<TopLeft>A_InnerFrameTopLeft</TopLeft>
<Top>A_InnerFrameTop</Top>
<TopRight>A_InnerFrameTopRight</TopRight>
<RightTop>A_InnerFrameRight</RightTop>
<Right>A_InnerFrameRight</Right>
<RightBottom>A_InnerFrameRight</RightBottom>
<BottomRight>A_InnerFrameBottomRight</BottomRight>
<Bottom>A_InnerFrameBottom</Bottom>
<BottomLeft>A_InnerFrameBottomLeft</BottomLeft>
<LeftTop>A_InnerFrameLeft</LeftTop>
<Left>A_InnerFrameLeft</Left>
<LeftBottom>A_InnerFrameLeft</LeftBottom>
<OverlapLeft>0</OverlapLeft>
<OverlapTop>0</OverlapTop>
<OverlapRight>0</OverlapRight>
<OverlapBottom>0</OverlapBottom>
</Border>
<Titlebar>
<Right>A_WindowTitleRight</Right>
<Left>A_ChatWindowTitleLeft</Left>
<Middle>A_WindowTitleMiddle</Middle>
<OverlapLeft>0</OverlapLeft>
<OverlapTop>0</OverlapTop>
<OverlapRight>0</OverlapRight>
<OverlapBottom>0</OverlapBottom>
</Titlebar>
</WindowDrawTemplate>