LDF is a transaction log file that SQL Server keeps for all updates on your database. In order for you to revert back these updates, you need your database first, otherwise there's nothing to be "reverted".
Find the latest backup of your database and restore it. Then use your transaction log to reflect the changes.
Here are some links that might help you.
http://sqlserver2000.databases.aspfa...log-files.html http://blogs.techrepublic.com.com/datacenter/?p=132
-- CK