How to change 'home' field for root site???

Hi

I’m having a nightmare trying to change domain name and integrate an existing blog into my multisite domain.

I’ve trawled through all the database tables and as many php etc files that I can think of and I can’t find a way of changing it anywhere.

I can for all the other sites but this ‘root’ one won’t let me edit it (or delete it).

Is it even possible to change the ‘home’ field as I know that is the only thing stopping everything from working successfully!