In which directory? Please do not delete it before you understand its use. Based on the file size, it should be transaction log file which is vital for disaster recovery. Without these transaction logs, you cannot recovery the system to the point just before the disaster. At the same time, a full backup will purge these transaction log files.
Please refer to http://www.microsoft.com/Exchange/techinfo/deployment/2000/E2Krecovery.asp for more information about disaster recovery.