Porting to Native WindowsNT/2000

I understand that the current port of Postgres for Windows requires the 
cygwin package.  I'd like to understand the requirement for cygwin,and 
possibly try to port Postgres to run natively on Windows as a NT/2K 
service.  Anyone like to identify the challenges in such a port?  Is it 
at all possible?  Anyone else trying to do this?

D