It's not possible to disable logging withing SQL Server. You can enable the use of non-logged functions, like WRITETEXT, but in general you cannot disable logging. Nor do you really want to. The information in the transaction log is used to restore the database to a stable state if the server were to prematurely go down (ie crash).

If you do not want to periodically backup the transaction log for recovery purposes, you can set the Truncate Log On Checkpoint database option. SQL Server will automatically remove terminated transactions (committed or rolled-back) from the log when the Checkpoint occurs (about once a minute).

HTH

-MIke