Apache has been ported to a very wide array of Unix boxes - in fact, we're not aware of any Unix boxes which Apache can't run on. This has been posible by making conservative architecture decisions, by modularizing the code as much as possible, and sticking to POSIX and ANSI wherever possible (and functional).
However, due to the code's legacy, and use of metaphors and systems which are Unix-specific (such as, having multiple processes all accept()ing connections to the same port), the road to porting to Windows NT has not been a pretty one. Several attempts have been made, both by Apache Group members and outside folks, but due to a lack of stability and a clear consensus on how to manage a true cross-platform development project, NT is not yet a standard platform supported by Apache.
This could change - in fact, our current plan for Apache 2.0 is to
put all platform-specific code behind a single interface, making the
job of porting a lot easier. In fact ports to Win95 and MacOS might
even be possible this way. Compile with plat_winnt.c to
use it on Windows NT, etc.
When will 2.0 come out? Not for a while yet - 1.2 is on its way to being finalized, and while 2.0 work has begun it'll be awhile before it's got all the features in 1.2, since we're working with a significantly revamped code base to allow for multithreading. But sometime in the first half of 1997, we hope - we have test versions of it running already.
In the meantime, folks interested in working on an NT port can send mail to apache@apache.org - when 2.0 work begins in earnest we'll probably start an NT-specific list to address porting issues.