Darcs unable to find executables registered via "App Paths" on windows platform.
For example:


D:\> darcs.exe send -v --sendmail-command="python"
...
'python' is not recognized as an internal or external command,
operable program or batch file.

darcs failed:  failed to send mail to: antispam@example.com

D:\> python
Python 2.5.1 (r251:54863, Apr 18 2007, 08:51:08) [MSC v.1310 32 bit (Intel)] on
win32
Type "help", "copyright", "credits" or "license" for more information.
>>>

It works for me. There's a GHC bug that makes runProcess ignore the current PATH 
env var, and make it use the "system" or "user" PATH env var. So if you add a 
directory in the PATH for the current shell and you execute a command with 
runProcess, it won't search in there.
If that's the case, it's not a darcs bug.

It is not the same. "App Paths" is a registry key with application paths.

http://www.codeguru.com/cpp/w-p/dll/article.php/c99