, HP's "passive IR receivers" aren't RC6/eHome/MCE sensors at all.
The actual definition of a "passive IR sensor" is essentially what you see in motion sensor lights/switches. HP has used the term a bit "off-label" here to describe an IR extender
system it has used in some of their chassis.
The sensor in your PC is likely built into the card reader and is supposed to be mated to a slot-fitted bracket (not an actual PCI/PCIe card but just goes in the slot), with other IR connectors for an extender system. It's called "passive" in some cases because they had both passive implementations and ones with "controller" electronics, depending on the intended purpose and what TV tuners might be bundled as options on a particular model.
When designed such that the TV tuner would have the "controller" the front IR receiver and rear ports (if applicable) would be "passive". In the other scenario the front IR would connect to a similar bracket, but one that had the "controller" (that likely connected to USB, the TV tuner, or some proprietary port, I'm not sure).
A further explanation (with pictures) is here:
So I'm pretty sure the front panel IR sensor in the card reader, on its own, isn't usable as an IR sensor for Windows purposes. Hence their use of the term "passive", despite it not actually being what is otherwise defined as a passive IR sensor (a motion detector).