Compiling darcs-2.0.0 on Windows which has GHC 6.8.2 installed, I get  
this error:

[ghc] src/Darcs/Resolution.o
[ghc] src/Darcs/Repository/Internal.o
[ghc] src/Darcs/Repository/Checkpoint.o
[ghc] src/Darcs/Repository.o
[ghc] src/Darcs/Arguments.o

src/Darcs/Arguments.lhs:88:39:
     Warning: Imported from `Darcs.Hopefully' but not used: `info'

src/Darcs/Arguments.lhs:89:65:
     Warning: Imported from `Darcs.Patch' but not used:
                `list_touched_files'

src/Darcs/Arguments.lhs:90:0:
     Warning: Module `Darcs.Patch.Info' is imported, but nothing from  
it is used,
                except perhaps instances visible in `Darcs.Patch.Info'
              To suppress this warning, use: import Darcs.Patch.Info()

src/Darcs/Arguments.lhs:94:0:
     Warning: Module `Darcs.Progress' is imported, but nothing from  
it is used,
                except perhaps instances visible in `Darcs.Progress'
              To suppress this warning, use: import Darcs.Progress()

src/Darcs/Arguments.lhs:107:17:
     Warning: Imported from `Printer' but not used: `renderString'

src/Darcs/Arguments.lhs:107:52:
     Warning: Imported from `Printer' but not used: `vcat'
make: *** [src/Darcs/Arguments.o] Error 1

real    1m28.537s
user    0m7.830s
sys     0m6.010s

Now I do have cygwin installed, and I am using cygwin bash to invoke  
make, but this should not be able to cause these problems.

Regards,

Zooko

Looking at the source code, I get the impression that this is happening because
WIN32 is not being defined.

Zooko, maybe you can fix this by editing GNUmakefile, which has a line GHCFLAGS
+= -isrc/win32 -Isrc/win32 -DWIN32

Actually, you should probably first look to see if SYS is being set to Windows.
 I see this line in configure.ac
AC_CHECK_HEADER(windows.h, [SYS=windows], [SYS=other])

I'm marking this as not-our-bug for now, since we only give compile instructions
for msys

I'm sorry I didn't mark this ticket before now, but this was fixed by:

Thu Apr 10 14:48:30 MDT 2008  zooko@zooko.com  * make darcs build on win32 by
conditionally compiling out a few bits that are unused or meaningless on win32