Randomly via the Lost Levels forums, I happened upon a pretty amazing guide to the Resident Evil 4 trial editions, over at the super-indepth 'The Horror Is Alive' RE fansite.

It's explained: "Shortly before the release of Resident Evil 4 in the United States fans were shocked to learn certain retailers were receiving stock of a very peculiar disc. Available only to those who pre-ordered, it was titled "Resident Evil 4 Preview Disc". Given away at most Gamestops and EB Games in the states, most of the stock was left unclaimed and therefore it was decided to simply give the disc away to anyone who wanted one."

He continues: "Less known, is the Resident Evil 4 Demo which was shipped to your home after purchasing the Resident Evil 2 pack, Pure Evil. More uncommon is the Nintendo Kiosk demo's which also contained Resident Evil 4 demos. So how many demos are known, and are any of them different? This article hopes to answer those questions." And so it does, over a grand total of 28 pages (!), with an insane amount of in-depth info - the site's other features also have some very cool otaku-like details, include several translations of Japanese-only RE backstory.

The most interesting thing by far is that the trial versions have been hacked, most notably to reveal removed 'Heat, Light, and Slow' effects that were left over from the semi-scrapped and adapted Resident Evil 3.5, which also included scenes in an airship, according to debug info - plenty more info about earlier RE4 versions on the Wikipedia page, for those not in the know.