Pure DLL (where embedded graphics hang out) removal is a registry key deletion set-- try looking in the registry guides at
http://www.winguides.com. EDITTING,unfortunately you get to find the resource file and edit the EMBEDDED graphics call code or embedded graphic itself from within DLL and I do not have a good handle on the exact software set one person I KNEW in France used to do this exact thing on his own box. That button, though, is part of an integrated dll and NOT a separate graphic laid in in a callable changeable way in registry, unlike the starting and closing graphics for Windows itself which are in fact separate files-- desktop icons are mostly seperate files also, though they can be embedded in dlls also if a programmer wants to make it a PITA to find and change them.
You could see if ResHack is still around anywhere, but I do not have a copy now. Except for taskbar, you can right-click and say delete most things that are not dll embedded graphics, I think the printer set is an exception to normal .ico use in start menu for 95 OSR2 and up and is registry entry defaulted in part and part in the start menu dll set (and I forgot the name, sorry, been too long since I played with that particular thing).
Note the full licensing of ResHack is not something you might want to do with a US address, though for your OWN boxes only and not for distribution you can use it legally for what YOU want to do. Microsoft does not say that editting the looks of your OWN box is illegal, but has copyrighted the look of what they require OEMS to distribute and the start button is part of THAT.
Also, on WinGuides.com, see if RegHackr still hangs around, if so he is an absolute WIZ with the registries for MOST windows versions, though in some ways stubborn about what is best single way to do things-- it would not surprise me if he helped WRITE the downloadable guides, they have his writing flavor in many places.
John.