I can see it in your eyes. You want to download a 2.9GB demo. No, really, you do. Because ta-da, the PC release of Burnout: Paradise goes shopward in the morning, and entire game is available to download, for free, in a time-limited way. Perhaps from Fileshack, perhaps from GamersHell. Or maybe from NVidia. (Actually, the servers are crazy busy at the moment, and hopefully they'll be echoed in a few more places. Post links below if you find them - but please, no torrents unless officially sanctioned.)
Burnout: Paradise has been out on consoles for 450 years, but the PC version isn't simply a belated port. It is, in fact, the most complete version of the game (although the consoles will catch up as the various patches are applied by whatever arcane means those demonic boxes use). All the free add-ons that have appeared since the original release are already in there (including motor-o-bikes), along with various gameplay and engine tweaks. And the first pay-for content, the Party Pack, is also bundled. RPS will be bringing you its definitive opinion on whether it all works out well very soon. In the meantime, we give you permission to form your own opinions via the entire game (while the demo lasts). Once time's up, you can pay to unlock the version you already have, making this possibly the largest shareware game of all time. (Go on - point out the bigger ones.)
Criterion explain it all in enormous detail here, but you'll note they're extremely vague on how long the demo version lasts. If any of us live long enough to download it, we'll let you know. If anyone else already found out, you let us know. We're friends like that.