I've searched and only found ppl asking about it. How do I make a 1 px border?
[help] 1 Pixel Border
You could edit the "frameCaption", "frameRight", "frameBottom", and "frameLeft" images inside an msstyle file to have the outside pixels be a different color than the rest.
If you mean reduce the images to one-pixel wide, then you could put "magic pink" where you don't want any image. I think I tried that once and got some funky results though...
I have a feeling Windowblinds may be a better choice if you haven't found any answers yet. I've seen some great work that just cannot be done with visual styles.
Anyway, if you're looking to edit the window frame images, those listed above should do the trick.
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