Is there a reliable crossbrowser way to open up a shell using javascript (e.g. explorer.exe)?
This is not possible as it would be a (gaping) security risk.
No, that is not possible for security reasons. Accessing client machine is the problme here !
If you have access to the client machine, and the client machines are all Windows XP or later, there actually is a way by defining a custom protocol as described in this SO question (Mozillazone article here).
That way, you can create links like my_custom_protocol://helloworld.txt
that cause an explorer window to be opened in Windows.
This potentially opens a (however remote) security hole, as connecting a custom protocol to explorer.exe
could be used to send arbitrary parameters to that executable. Make sure you are aware of the security implications; depending on your situation, it might work for you, though.