It is wxWidgets-2.8.7, statically linked.
There are KDE, Gnome, Vista (no aero, can't enable it under vmware), Windows 98 and XP.
It is really portable and really easy to compile, but it looks a bit ugly.
Obvious problems:
1) Sizing has no limitations. I.e. in vs2005 (Whidbey) you can't move splitter
out of the window area, like you can in wxAui. Should be fixed. It's on any platform.
2) Venetian Blinds (ugly jalousie feature). I'm sure it should be replaced to rectangle
hint if there is no transparency support. Also, it seems there's no appropriate brush handle
in windows 98 so it draws it white. And this "glossy theme" for tabs... come on, who likes it? The "simple" one looks much better.
3) Toolbar color problems (win98, vista). Should be fixed (I beg you, at least for Vista).
And the toolbars... a way too rough. I mean even paint.exe looks better.
4) Toolbar glitches. "Sample vertical toolbar" is double size in windows,
but regular size in KDE and Gnome. I don't know the real case, but it's suspicious.
Images are linked to picasa, where you can view it in original size (up to 1280x1024, press magnifying glass button there).

KDE, Venetian Blinds

Gnome, Venetian Blinds

Windows XP, splitter's gone for a walk

Windows 98 - no brush, no colors

Windows Vista, toolbar problems