I will try to find some details, as HP's site doesn't give informations about the TV tuner, just the existence of it in your PC.
As the ideea is to have a cheap media center PC, probably the tuner it's based on BT 878 A or on the newest 23880. I will check for capabilities and return.

LE: 2388x chipsets allow a maximum capture resolution of 768x576 and I believe 878 is the same. Probably at this moment my advices are:
1. to swiich the rendering method from overlay mixer to WMR 9.
2. to reduce the resolution in BSPlayer's tuner window to 768x576

Maybe someone from the team can tell us something about any limitations in accessing tuner capabilities.

i tried to switch to a different overlay, but it didn't work. changing the resolution made it worse.

So, at 1024x768 looks interlaced, at 800x600 looks...how ? and at 768x576 ?

i'll get back to you (sorry, i have school now).