There is only one file type that uses the .TXN extension:
MySpaceIM Conversation Log File
Log file created by MySpaceIM, an online chatting program; stores all online conversation messages with a specific user; used to keep a chat record that can be reviewed later.
TXN files are saved with the naming convention user.txn, where "user" is the name of the person that was chatted with.
Updated: March 7, 2010