Yahoo Message Archive Decoder reads Yahoo! Messenger archive files (.dat files) and presents them in a format that you can read.

1.Decodes the message archive without logging in.
2 No passwords required.
3 .Supports Unicode text (Chinese,Persian, Arabic , Japanese, and all non-latin characters).
4. Decodes normal conversation messages, private messages, conferences, and SMS/Mobile Messages , complete with time stamps
5. Up to 20 times faster than the Yahoo! Messenger internal viewer.
6. ONLINE & FREE!

Normally, you must be logged in to Yahoo! Messenger (using your or someone's password) to view the Message Archive. However,

If you forgot your password, but something important is in the archive (telephone number, business contact, email address, etc.)
If you want to search some text deep hidden in a bunch of archive files.
If you want to spy other's conversation or SMS (your kids, your spouse, your employee, etc.)
If you cannot stand waiting the slow Yahoo! Messenger internal archive viewer
If you want to save or backup your conversations completely with smilies