[User9812]

That page doesn't load correctly on my desktop, so I can't see the example.

Your question though, you want to show the first few minutes of the video or something along those lines, then ask users to register?

That'll definitely increase registration. I don't agree with it though. You'll inflate your registration numbers, and at the same time, turn away users from enjoying your content. For example, Quora displays a portion of comments, then blurs the rest asking you to sign-up. I know you can get creative and modify the URL to get the full page, but I just no longer visit links to Quora based on principle. I don't like to jump through unnecessary hoops.

You want users to register, because they want to register. You can hold their video hostage after the preview, and they'll just create a throwaway account, or register, and never participate or return. Is that something you want to encourage for the ego boost of a higher user count?

Anyway, that's my take on the situation. I'm always for giving users the best experience possible, and I think interrupting their video doesn't achieve that goal.