Boredtoday wrote detailed version of this here!

So, the full tuto goes something like this:

1. Remove (uninstall) Network Profile application and remove any APN you set up in settings -> cellular.
2. InterOP-unlock your device (Heathcliff)
3. Install DiagProvXML app
3. Using Isolated Storage Explorer deploy enclosed provxml files
4. Install the xml files in this order: hotspot, hotspot1, mxip_hotspotconfig_01, EnableAutoDataConfig
4b. Check in settings that you can now see Internet Sharing between Bluetooth and accounts!
5. Reboot
6. Deploy WP7 Root Tools (Heathcliff)
7. Now launch Root Tools and go to Local Machine -> Comm -> InternetSharing and manualy add:

Name => value (type)

EntitlementURI => ./Vendor/MSFT/Registry/HKLM/Comm/InternetSharing/Settings/OpenMarketEnabled (string)
OpenMarketEnabled => 1 (dword)

8. Clear "CellularConnectionName" (aka set to empty)

and you can go to settings -> Internet Sharing and start it up

// Oh and I had some problems with it when system was set to CZECH. When I HRed and did the same process in English, it worked fine ?!.

// You can also try my all-in-one provxml file on - deploy it via the Isolated Storage Explorer to the diagprovxml application and after running it, reboot the phone. I am not testing it, I already reset my phoe 5 times today. Sorry
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