Here are some notes I took about building hpcboot.exe from NetBSD 2.0
sources:

1) apply http://backyard.homeunix.net/~ben/docs/comp/unix/netbsd/patches/2.0/do_subst.sh.diff

2) cd /usr/src/sys/arch/hpc/stand && make evc3

3) somehow transfer /usr/src/sys to Windows XP Pro system
(I used ffsdrv.sf.net on my dual-boot system)

4) download The Windows CE eMbedded Visual Tools 3.0 (and Product ID!) from:
http://www.microsoft.com/downloads/details.aspx?familyid=f663bf48-31ee-4cbe-aac5-0affd5fb27dd&displaylang=en

5) download and install Handheld PC Professional 3.0 SDK
http://www.microsoft.com/downloads/details.aspx?FamilyID=B75DB4FB-1AED-4B45-AF62-3C38AC8A1EA7&displaylang=en
after running SDK.exe, I had to manually run C:\HPC30\Jupiter SDK\SETUP.EXE

6) open hpc_stand.vcw, select appropriate platform and target, then
press F7 to build hpcboot.exe

7) find hpcboot.exe under sys/arch/hpc/stand/compile/, and it worked!