Actually, after investigating this further, I found the following ([read more here](http://msdn.microsoft.com/en-us/library/aa365247%28VS.85%29.aspx)):

> Note  File I/O functions in the Windows API convert "/" to "\" as part of converting the name to an NT-style name, except when using the "\\?\" prefix as detailed in the following sections.

I think this means we should accept a path starting with `/` as an absolute path on Windows.