The S-VIDEO port on the Inspiron 9400/E1705 is actually *NOT* an S-VIDEO port, but a *GENERAL PURPOSE* port in the shape of an S-VIDEO port.
By default, yes, if you plug an S-VIDEO cable in there, it's going to do that. But Dell makes several connectors for various other protocols. I believe that it's also capable of outputting digital audio (S/PDIF) via the same port, for example.
You'll notice that while an S-VIDEO port/cable has four pins (of which two and two carry the same signal so really it's four pins but two signals), the port on the notebook has seven.
This is fairly standard on computer S-VIDEO ports (where they're 7-pin S-VIDEO variants), as they'll use four pins for S-VIDEO and the other three for Component. I'm not sure where S/PDIF fits in, but I do recall reading that it was supported. Assuming it is, that'd mean that the port on the notebook isn't just an S-VIDEO variant.
Anyhow, that doesn't matter, the point is that yes, the notebook CAN output an actual HD component signal from that port. You're not going to do much better (if at all) with a VGA to Component adapter, and you WILL pay a small fortune for those types of devices.