OK, all sorted now!
I finally got ProgDVB v. 4.73 up and running on PCTV 400e USB... importing TuningSpace.reg into the registry was the first thing... but I also needed to add an extra library file (PclePctv400e.dll), and 3 extra modules (BDA.device, DVBSTuner.device, and IsAvailable.device), all downloadable from the following site:
h**p://pctvsat.free.fr/viewtopic.php?t=2684&sid=7de59f87c9105249cfcb4330f8271d9b
once you got all you need, the setting-up is actually quite straight-forward:
1) you just need to install ProgDVB without selecting any card mode (just choose the --not start device-- option), check Register Elecard filters for software mode, and finally choose not to start ProgDVB after installation completes
2) once you've installed ProgDVB, copy the PclePctv400e.dll library file in the C:\ProgDVB folder, and copy the 3 extra modules (BDA.device, DVBSTuner.device, IsAvailable.device) in the \Modules subfolder
3) start ProgDVB, select Settings -> Device List, and Start DVB LifeView... then, you should be able to start DVB-S Tuning-Space (BDA.device)
(if DVB-S Tuning-Space doesn't start, try stopping DVB LifeView: sometimes you just needle to feedle a bit with this setting... but eventually you should be able to start the BDA device)
and that's it: once DVB-S Tuning-Space is started, the reception quality level will be displayed... so you can finally select your satellites, and perform a scan...
ProgDVB works so much better than Media Center, i'm so glad i can finally get rid of Pinnacle's software!