On Windows XP, Ruby 1.8.5:

# start notepad
irb(main):003:0> info = Process.create :app_name => "notepad"
=> #<struct Struct::ProcessInfo process_handle=1916,
thread_handle=1912, process_id=3536, thread_id=3088>

# notepad running
irb(main):004:0> Process.kill 0, info.process_id
=> [3536]

# kill notepad
irb(main):005:0> Process.kill 9, info.process_id
=> [3536]

# notepad's dead, but why doesn't this throw an exception?!
irb(main):006:0> Process.kill 0, info.process_id
=> [3536]

Any ideas?
Thanks,
Joe