First thing to check is to ensure that your Antivirus (AVG, nortons, etc) is not removing Files and quarantining them on accident.

There should be two copies of eventlog.dll, one in sys32 and
one in sys32\dllcache.

If one is missing copy and paste from the other. If both are missing
try to get them from either your installation disk or one of the many
download sites.

After these files are in place start services.msc, click on event log
and click start.

Also be sure it is set to automatic so it always fires
up when you reboot.

Your logs should now display unless some other bug
has occurred.