Windows logs a lot of events and these entries grow over time. If finding particular entries to troubleshoot gets difficult, you can delete them all and start over so new entries are easier to peruse. I have done the following on a Windows 8 machine, but this should work with any Windows OS with powershell.
To delete all the event entries, start the powershell with administrator access, and type:
wevtutil el | Foreach-Object {wevtutil cl "$_"}