Virgin Media have the first six episodes of The Sopranos available On Demand in "High Definition". I know that from the second season the show was filmed in HD (see story here) but was unaware the first was available in HD. Dates from 1997
Also the pilot of ER is listed as HD. I watched this last night and I don't think this is high definition either. Cracking bit of TV, but it dates from 1994 and unless it was shot on film I suspect it's been upscaled. According to Wikipedia:
ER is unique in that the series was filmed in 16:9 anamorphic widescreen from the start, even though it did not air in widescreen until the seventh season when it began appearing in the 1080i HD format where NBC was being broadcast digitally.Anyone know more?
[see comments below for an update : ER is SD, but The Sopranos is high definition...and looks great!]