In the early 2000s, most people in the US didn't have HDTVs, much less a good way to buy high-definition movies. We were lucky to have standard-definition DVDs! In 2002, an oddball format called D-Theater delivered HD video on Super-VHS tapes. This was accomplished in part by playing the tape at high speed, which generated so much heat that a giant fan had to be bolted onto the back of the player. In any case, the quality was (and remains) stunning, given the tech available at the time.
The whole system was encrypted and copy-protected out the wazoo, the player machines were costly, and of course HDTVs were still multi-thousand-dollar items. Oddly, the whole format died years before Blu-ray and HD-DVD debuted—leaving a gap in the HD-movies-at-home business that would mostly be filled by cable TV and DVRs.
Here's a detailed run-down of how the whole thing worked, including demos with movies including GalaxyQuest and I, Robot (the last movie released on the format). Enjoy: