Here is a link for you Rafael.
http://www.cisco.com/en/US/products/sw/voicesw/ps2237/products_maintenance_guide_chapter09186a0080443807.html#wp1074751
Since circular logging is not enabled by default in Exchange 2000/2003 these logs files will continue to be generated. Only a Exchange aware backup utility, Backup Exec or NetBackup Cisco recommended with Unity, will remove those log files. Check on Cisco site for version information. The DIRT utility included with Unity does not have this capability.
The only Cisco recommended solution I know of is to run the recommended backup software. You can move these transaction logs off the Unity server manually if your in a spot :). Be carefull doing this and make sure not to delete them until the Unity server is rebooted and tested. I would keep a weeks worth if possible on the Unity server and move the rest of the log files off box. Make sure you only move .log files. They should all be 5MB.
These transaction logs are used to recover an Exchange server. If it is not possible to run an Exchange aware backup utility on the Unity server you might want to look at enabling Circular Logging on the Exchange Storage Group.
-Ryan