Since a few people have asked me about this, I thought I'd pass on this information.
Microsoft has said that the 'Internet Sharing' feature on Windows Phone 7.5 'Mango' will currently only available on new handsets running 'Mango' out-of-the-box for now and that in the future it might be rolled out to a selection of older handset.
However, over on Windows Phone Hacker there's an easy way to get the tethering feature enabled Samsung Focus and the Omnia 7. And it seems simple enough:
- Download DiagProvXML and Samsung Tools
- Deploy both XAPs to your phone
- Run DiagProvXML and hold down on the Internet Sharing item, press Execute
- Close (press Back) DiagProvXML, and run Samsung Tools. Press Apply to set Auto Data Config.
- Your phone will reboot, and everything should work from there on it.
If that's no clear enough, there's a video:
WARNING: This is an unofficial hack. Things may well go wrong, and if they do, don't expect support!
(Hat tip to Long Zheng.)