>>Right click on your database in SSMS Database tree. On the Database properties form, select Options. You can change the Recovery model to Simple which sets minimum logging. Keep in mind that you'll need good database backups because you won't be able to recover from the transaction log.
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>It is already Simple. The MDF is 21 MB. The LDF is 24 MB. This is way too much. Also, as I said, in the development PC, this takes place for nothing. Isn't there really an option to turn that OFF? Also, what would be the relation, as you mentioned, in regards to backup. When the backup is done, we backup MDF. If we adjust the log, what could be a factor here?

Try to truncate the log. If your recovery model is simple, it means you can not restore to the point of time, you can only restore to the time your last backup was made.