What is the large open space for to the right of the hard drive when looking inside a 5400/5500 from the back panel? There seems to be a spare power cable or something, but no other connectors that might attach to anything...
LCGuy has nailed it. NTSC (N.Am.) or PAL (Aus.) tuner, and the ribbon cable is for power and signal. There are usually a few kits with tuners (some with NTSC TV and FM) floating about eBay, often NIB. See, eg, fuzzstjohn.
If you have a good look in there, you'll see that there's some rails in where that plug is, those rails are what the TV board goes into, to hold it in place.
