How to Clear up CertLog

Active Directory Certificate Services transaction log files
When completing a critical or system state backup of the C: volume, a new transaction log will be generated under the c:\windows\system32\certlog folder.
Removing these logs is only safe as long as the CA database file is consistent. In order to remove these logs and reclaim disk space, follow these steps:

1. Open the Services MMC and stop the Active Directory Certificate Services service.
2. Make a backup copy of ALL the file contents present in the c:\windows\system32\certlog folder.
3. Delete EDB.CHK and all the files that have an extension of .LOG (*.LOG)
4. Restart the Active Directory Certificate Services service.