http://www.hauppauge.co.uk/site/prod...a_hvr1100.html, we list 2.8GHz as the recommended minimum CPU for watch analog. You can get it to work with less CPU, but you'll probably need to enable game mode, and tick the 'disable game mode recording' option, then reboot. Be warned though, after doing this you loose the ability pause/skip/record. To have all software features available, with a software encoder card like this, you really need a faster CPU (so you can run with game mode disabled).
If you're watching digital H.264 channels, you need the WinTV HD version, which comes with H.264 decoder. Decoding high definition H.264 channels is very hard on a PC, and often requires hardware acceleration to be enabled, and the user to have an nvidia 8500/8600 or higher video card that supports hardware H.264 acceleration.