Is there any possibility to edit the registry on a Nokia Lumia 800? I know there are options to get one on HTC devices but it seems there is no for Nokia phones.
There is a thread on the XDA forums, and it looks like it is possible. I don't have an L800 to test it, but the aforementioned link does give you some instructions on how to do it. Links are also included on unlocking your phone, and installing the Root Tools. For bonus points, the thread also includes some key registry changes you can make.
Proceed with caution Should you brick your phone, or otherwise screw it up, I wouldn't count on getting support from Nokia or your carrier.