.mdf is the database file for SQL

the transaction logs are .ldf

i have checked both my production and testing .
both show me both database and log are in extension mdf

I have heard of them being bundled together into a .bak file but never a .mdf

What version of SQL are you running?

How SQL creates it's backup files has no bearing on the version of EV

Attached is the screen capture .

currently using MS SQL 2005 Standard Sp2. X32 bit

The Enterprise Vault Audit and Directory database and log files are always created with an MDF file extension instead of the generally accepted MDF for the database file and LDF for the log file.  This behavior has no impact on the performance or functionality of Enterprise Vault, however, it is possible to manually rename these files by following the steps outlined in technote 307876

Please refer following documents which describes this behavior

http://support.veritas.com/docs/320498 - The Enterprise Vault Configuration program creates the Enterprise Vault Audit and Directory SQL databases and logs with a file extension of MDF

http://support.veritas.com/docs/307876 - Can the file extension of the 'EnterpriseVaultDirectory' SQL Database Transaction log be changed from MDF to LDF?

this has been the case for a long long long time and is a frequent issue for some users, it doesn't really matter or make a difference though
you can call the database and log files any extension you want, such as EnterpriseVaultDirectory_db.Bert and EnterpriseVaultDirectory_logs.Ernie

Here is a link to the doc stating this is a known issue and that it does not affect functionality
http://support.veritas.com/docs/320498

You can subscribe to the doc to be alerted when the issue has been addressed.

It has been an issue which has been around for a long time unfortunately, but it doesn't affect anything.