After doing a full backup of the SQL database, go into Enterprise Manager, drill down and highlight your database, right click, all tasks and choose shrink database. There's a button that will let you shrink the database file seperately from the log file or shrinking it from the first screen will do both. If it is having problems shrinking the log file, right click on the database, choose properties, options tab and set the recovery mode to simple. Then repeat the shrinking steps. After it's done, set the recovery model back to full.
If you have the recovery model set to full, make sure you have a database maintenance plan that's doing a periodic full backup along with backing up the transaction log files or your log files will just grow, grow, grow.
Kevin Scheeler