I am getting an error about the log not being a valid Exchange 2003 message tracking log.

You are most likely scanning the wrong logs. ELA will only scan message tracking logs.

You can find out where Exchange stores these logs by:

• Open the Exchange System Manager
• Find your server under Administrative Groups > First Administrative Group > Servers > Your Server.
• Right Click your server and select Properties
• Look at the "Log file directory" label to see where the logs are being stored.