Restrict Characters in username?

[ps2wiz]

When members register, how do I restrict user names to the basics such as only letters, numbers, underscores, and periods?

Thanks.

[Brother Malachi]

If you look in vBulletin Options, under "User Registrations" you'll find Username Regular Expression.
It uses the php function preg_match. If you google "preg_match letters, numbers, underscores, and periods" you're bound to find the regular expression you're looking for.