The pattern in most environments is the %windows% directory, %system32% ... etc. There are other w3 formatted directories under \LogFIles -- but primarily most folks will be looking under this directory for what they need:
C:\WINDOWS\system32\LogFiles\W3SVC1
Once you're there, the actual log files will look like:
exYYMMDD.log (e.g. ex080802.log)