Here is the update:
Win 7 loads and works fine. GeForce 4 does not pass DCA, neither does 2 GB of RAM, nor the single core Sempron processor.
Adding Radeon 4350 AGP card freed up 512 MB of RAM and made it pass DCA in terms of Video and RAM. CPU still does not pass.
DCA override allowed me to connect to Hauppauge 2650, and get it working, sort of. It records, and plays back just fine, but watching live TV is un-watchable; lots of pixelation, tearing, skipping and jumping: 100% CPU utilization, and really really sluggish response to any commands.
Next step is to purchase AMD Athlon XP 3000+ (fastest CPU supported by the motherboard) and repeat the experiment. Luckily, those processors are so obsolete, they are $13 on Amazon!
I dread dealing with PlayReady not updating, which is most likely to be triggered by CPU swap.
6 TV's in the house on FiOS and we only pay $4.99/month to connect them all!!! Power to the CableCard and WMC7!!!