For example, to handle a new header file (similar to source files) with extension .abc:
Create key:
HKEY_LOCAL_MACHINE/SOFTWARE/Microsoft/VisualStudio/8.0/Languages/File Extensions/.abc
set default value to same as .h key --> {B2F072B0-ABC1-11D0-9D62-00C04FD9DFD9}
Modified value ExtHeader at
HKEY_CURRENT_USER/Software/Whole Tomato/Visual Assist X/VANet8
to --> .h;.hh;.hpp;.hxx;.ipp;.tlh;.inl;.p;.rh;.dh;.ih;.ph;.abc;
No need to rebuild or make any changes in the options or customize dialogs.