Check to see if username is valid

[wrongful]

I am working on a script that needs to check to see if a username that a person types in is a valid user registered on the forums. Is there an easy way to do this?

Edit: oops, should have been in general modification discussion.

[Xenon]

*moved*

well, the easy way is to do a query on the usertable, seraching for a user with that username, and if the query returns anything, then it's valid :)

SELECT userid FROM user WHERE username = 'username here'