I'm not sure I understand this change... perhaps I'm missing the relevant background.

* This file is already in `reboot/windows/` so is guarding the requires necessary?
* Is the existence of an `ALT_SEPARATOR` the best way to guard for Windows?  There are some other methods I've used in the past, like this guy

```ruby
require 'rbconfig'
is_windows = (RbConfig::CONFIG['host_os'] =~ /mswin|mingw|cygwin/)
```