Modern Windows machines, when running for a while, often accumulate many gigabytes of log files, and they are often extremely fragmented over time. Recently I have found a log file of just ~110 megabytes with more than nine thousand (9,000!) fragments, and several multigigabyte files with four and five thousand fragments.

Below is a globular list of satisfactory purges so far found. Do be aware that you should only do this when you know that you do not need their contents!

C:\Program Files\Windows Small Business Server\Logs\MonitoringServiceLogs\*.log
C:\ProgramData\Microsoft\Windows\WER\ReportQueue\AppCrash*\*.tmp.*
C:\Program Files (x86)\StorageCraft\ImageManager\Logs\*.log
C:\Program Files (x86)\StorageCraft\ShadowProtect\Logs\*.log
C:\Program Files (x86)\StorageCraft\ShadowProtect\Logs\*.txt
C:\Program Files\Update Services\LogFiles\*.old
C:\Program Files\Update Services\LogFiles\*.log
C:\Windows\inf\setupapi.dev.log
C:\Windows\Logs\CBS\CBS.log
C:\Windows\Microsoft.NET\Framework*\*\*.log
C:\Windows\Microsoft.NET\Framework*\*\*.old