This is the change I would recommend making to the inventory window:
Add:
<InvSlot item = "InvSlot0">
<ScreenID>InvSlot0</ScreenID>
<!--<Font>3</Font>-->
<RelativePosition>true</RelativePosition>
<Location>
<X>0</X>
<Y>0</Y>
</Location>
<Size>
<CX>0</CX>
<CY>0</CY>
</Size>
<Background>A_InvCharm</Background>
<EQType>0</EQType>
<Style_VScroll>false</Style_VScroll>
<Style_HScroll>false</Style_HScroll>
<Style_Transparent>false</Style_Transparent>
<!--<TooltipReference/>-->
</InvSlot>
And of course the appropriate <Pieces>InvSlot0</Pieces> at the bottom.
This is of course just a stop-gap measure to take until your inventory mod gets
fixed properly by the author to actually include the charm slot
Also.. if you're not getting incompatable errors - you don't need to even bother changing your inventory window
Edited to correct case in Pieces section, as xml is case sensitive. - Cairenn
Edited to fix the stupid > being missing from the comments.. bleh!
- Remelio
Editted to remove to many -- in two places (should be --> not ---->) XMLspy caught this one - Kudane