Hello, I'm a hardcore X user forced into Windows. I wonder
is it possible at all to have multiple windows bound to a single frame under Windows ala PWM:
http://modeemi.cs.tut.fi/~tuomov/pwm/
Does anybody know of a project implementing such notion
for Windows?

It's unlikely. LS isn't really a window manager since Windows has a built-in WM that can't be changed. We've been able to extend the Windows WM in a few ways, but the feature you mention would be too difficult without the ability to completely take over the WM. Then again, maybe one of the other coders has some ideas.

Actually, it might be possible to stack windows exactly on top of eachother and add some kind of tab control to switch between them. It wouldn't actually do this (because, as Maduin says, it's impossible), but you could easily pretend it was.

I don't know of any such project tho...

I greatly appreciate your replies folks! The most useful
part of multiwindow frames is that I can see the titlebars
of all stacked windows side by side. And those can be made informative by showing current directories or currently
running programs (e.g. "Build..."). This way screen real
estate is not wasted like it normally would be.