I have this exact same problem only this was not an issue until WMC did an update (not my choice, accidentally must have allowed it to update). I've found the most common causes of microsoft issues are irrelevent updates that in turn throw the very unwelcome spanner in the works. I've had TV working through my PC for the last 8months without a problem.
Connection is Digital STB- RF loop to AVerMedia H751 Hybrid Analog /DVB-T tuner card RF input at rear of PC. As well I have S video cable from STBto S video input in tuner card. Granted the tuner card is old but as I've stated it's all been working fine. When this issue started I tried to rescan for my channels and came accross the " NO IR HARDWARE " **** again.
I seem to remember that I had this when I first set-up my new PC and fixed it by realising I hadn't inserted the USB (thing?) not sure what it's name is but it's a small, black plastic USB stick, (10mm)is all that extends from socket when plugged in. I originally thought it was just a blank USB plug to stop dust getting into unused ports so left it in the box when setting up. Anyway it all worked fine and has been for as I said 8 months. When I go into the TV set-up in WMC I receive a signal through the S video. I should also point out that the STB and television are working just fine, clear as a bell, no signal issues there. I try to set-up and scan and like all the others that seem to have been dealing with this since 2009 I am stalled at NO IR HARDWARE DETECTED. I've been into device manager and updated drivers even though there were no issues ! detected in DM, no hardware changes detected, running the latest drivers, I'm at a loss as to what to do now. The remote also is working as with yours it changes the volume and functions inside WMC, so the device is being picked up and functional but just NOT DETECTED ???????
Why does Microsoft not just install the original program that comes with the TV card, which might I say has all the same (simillar) features and more (troubleshooting QA etc) rather than issue people with a half baked program of thier own that is not at all user friendly and requires third party download fixes that are also not reliable and specific to this issue for all cards!
I'm a single parent of an 11yr old daughter and to keep the peace on the issue of what we watch on TV, I watch on the PC and she gets the TV and it's worked out fine, we're both happy and in the same room (I've get to wear the headphones) but we still interact and often end up watching the program the other starts to watch. ANYONE PLEASE ??