I think he's asking why there aren't more themes so the dll doesn't have to
be changed or using a 3rd party app.
Exactly.
I know about StyleXP and the uxtheme patch, but it seems ridiculous to
me that Microsoft would create a skinning engine for XP and then only
offer one skin in three colors, with no officially sanctioned way to
create or customize skins. You have to hack the OS or buy third-party
software in order to exploit the feature.
I just noticed the "More themes online..." selection in display
properties, which, despite its name, does not take you to where you
can find more themes online. Instead, it takes you to an ad page for
the XP Plus Pack. I suppose the real reason themes are locked down is
that Microsoft thinks the $hundreds you paid for XP wasn't enough.