Quote Originally Posted by nihil
No, it is a relational database and that is a key field............mess with that and it will screw up............ threads, posts and stats wouldn't stack up
The username will be a unique field, but probably not a foreign key (that'll be the user_id or whatever vBulletin uses - it's been a while since I used that particular piece of software). So in theory you should be able to change just the username and that will show up correctly everywhere, although you won't be able to change it to an existing username. Even if it didn't, an admin should be able to resyncronise everything with a couple of fairly simple SQL queries (I know because I've done it in the past, though not on AO obviously ).