SQL 2008 R2 creates user/schema when Windows user creates tables
This has always happened, back to SQL Server 2000.
Without schema, how does SQL Server know you want to put it in the dbo schema?

The only way to specify a default schema is to :


use SQL logins (not Windows)
run as "sysadmin"


Neither of these is acceptable

Best practice is to always qualify schema for every object reference for DDL and DML. There are clear performance benefits because of plan re-use.

Also, deliberate schema use is better for SQL Server 2005:


tables in Data
other tables in Archive, Staging etc
code in schemas per client permissions: Desktop, WebGUI etc


Using the dbo schema is so last millenium :-) Links:


Schema design - best practices?
https://dba.stackexchange.com/q/7257/630