when i watch HD on my tv (dvi input), it shows (on a pop up display) that it is at 1920x1080i. I've heard that it has a native resolution of 1920x1080, hence the info window that pops up.

now, i've been reading some articles and most plasmas seem to have native resolutions of 1280x768.

recently, the baseball playoffs on Fox have been advertised as being broadcast in 720p (if memory serves me correct). if my native resolution is 1080, then how is 720p depicted? is my tv down converting?

"non-square pixels".

Either way, when a 1080i image is being displayed on a lower-resolution device, it's being downscaled.

Fixed-pixel digitial display devices <i>always</i> run in their native resolution. Stuff that doesn't match pixel-for-pixel is either up- or downscaled.

..but the fed signal is usually a lot less than that due to limited banwidth. It's often quite a bit less than 1280x768, psrticularly on HBO and other movie channels.