Not easily.

   Your best bet is probably to run Linux and possibly WINE.

   If you REALLY want to run Windows, you could try searching for a
PocketPC or DreamCast emulator for linux, and then install Windows CE in the
emulated environment.

   - Oliver

Steve Jobs said Apple is abandoning the Power PC for the Intel CPU
architecture.  So if you wait a bit, the answer should be yes.

A PowerBook is indeed a very nice machine, but you're going to want to
run OS X on it. You can run VirtualPC if you want to test your Java
applications in a Windows environment, but don't expect great
performance of VirtualPC, it is after all an emulated environment.
But don't worry, once you've worked with OS X you won't want to go back
to Windows. Give it a try, it's truly a very nice operating system. And
as Roedy already pointed out, Apple is switching to Intel processors,
which should make it a lot easier to run Windows on an Apple machine in
the near future.
Also, Apple has recently registered a pattent that would allow for
running Windows and Linux at (nearly) native speeds as a virtual
machine. This would really be great news for us Java developers, since
you can then test your applications in the 3 major OS's, all on the
same machine!
For an article on the patent, see:
http://www.architosh.com/news/2005-11/2005a1108_tb-multi-os.html