Right. I actually use that exact HP receiver myself. What I meant was, if you don't have line of sight to the HP dongle, then a RF remote (like the one I linked you to) comes in very handy. When it comes to RF, Harmony is way overpriced. I, like you, don't have line of sight to my reciever, because it is in a coat closet with the rest of my A/V gear. The RF remote works up to 100' away (basically throughout most of the house, which is nice when listening to music while doing chores). I have had that exact URC RFS200 setup for 5 years without problems, despite it being repeatedly dropped by family members. It has even come apart multiple times, and once put back together, keeps working fine. I can't say enough good things about it. Just look at the reviews on Amazon.
I wasn't questioning the Harmony's ability to control your HTPC and other components. I was merely stating that IR without RF doesn't always work for every setup. It almost never works in setups that I do for clients, because they usually want their AV gear tucked out of sight, which means either using an IR kit, or an RF remote.
There is a fairly new product out, that I just used for the first time in a doctor's office waiting room. I put a Acer Revo 3610 (my old one) with XBMC in their server closet. I ran 2 cat5e cables from the server closet to the back of the TV in the waiting room. I used this
HDMI / IR over Cat5e wall plate kit from Monoprice, and it worked flawlessly. Cat5e is fairly cheap, as are short HDMI cables. IR kits used to cost ~ $100 alone. This kit is a game changer in my industry. I was very skeptical because of the $25 price tag, but they are watching 1080p mkv BluRay rips on the 50" LED in the waiting room, and controlling XBMC by pointing the remote at the IR receiver, which is stuck to the front of the TV. They think it's magic.
Hopefully this will help you with your unique situation.