Looks like James got it right...sounds best in E-minor (of course). The riff is pretty simple, looks something like this:
A|------2---x-x--5---0---| |-------2---x-x---5-3-2-0---|
E|---0--0---x-x-----------| |---0--0---x-x---------------|
Not quite the easiest thing to read, I know.