Film fans in the UK will soon be able to legally download and keep blockbuster movies for the first time, according to film studio Universal.
King Kong will be among the first films available on the service
King Kong and Pride and Prejudice will be among the first films available from the new service on the AOL website.
Fans will pay £19.99 for a DVD of their chosen film plus two digital copies to keep indefinitely - one for their home computer and one for a portable device.
Universal said it could "completely revolutionise" how people watch movies.
However users will not be able to burn copies of the films to DVD themselves and the files will be compatible only with PCs and Windows software.
That means they cannot be viewed on Apple iPods or Macs.
Last month, another UK website, Wippit, started offering permanent downloads - but only independent movies are currently available.
Other sites offer Hollywood movies - but only allow customers to keep the digital files for a set time, from one day to a month.
Universal Pictures UK chairman Eddie Cunningham said this would be the first of many such announcements and digital films would become available in many different ways.
"I think what you're seeing here is the beginning of a revolution in terms of how we can distribute digitally and I would expect you'll see a lot more news of this type over the next few months," he said.
He said his company just wanted to get its movies out to the widest possible audience.
Consumers felt "much more comfortable" if a DVD was included in the package as well as the downloads, he said.
"The statistics said people were three times as likely to pick up on this service if the physical copy was included as part of the bundle, and that astonished us."
Arash Amel, senior analyst at industry journal Screen Digest, told the BBC News website the Universal move was "excellent" for the consumer.
The service is not compatible with iPods
"I think download-to-own is possibly one of the most exciting developments for digital movie downloads over the PC," he said.
The UK movie download market is expected to be worth £200m by 2010, he said - with 40% of that coming from permanent downloads, he said.
The fact that films can be watched on a portable device is also a "major breakthrough", he said. "This is not the norm. This is quite a major step forward."
But studios must allow fans to burn films to DVDs themselves to allow greater flexibility and let prices come down, he added.
'A good move'
"I honestly think that the market won't grow to the same degree if they don't start offering that also.
"It's an exciting time but there are still issues that have to be addressed if this is going to really take off."
Paul Jackson, principal analyst for technology research company Forrester Research, said it was "overall a good move".
"I can see those portable video player consumers taking to this as an easy (and inexpensive, if they were going to buy the DVD anyway) way to get legitimate content onto their devices," he said.
But he added that because the service uses Windows Media Player 10, "it won't work with the video iPod or Sony's PSP, top contenders for portable video playback, or with a Mac PC for that matter".
And Ian Fogg, broadband analyst from Jupiter Research, said the service would only be successful if the price, release date and viewing experience could compete with other ways of watching the same films.
The service will be offered by Universal Pictures UK and DVD rental company Lovefilm via the AOL.co.uk website from 10 April.