"Allow Indexing Service to index this disk for fast file searching"
I believe since Windows 2000 server days you can take advantage of Indexing Service that creates indexes of the contents and properties of all files on local and network drives in order to increase file searching speed. It's quite similar to "Find Fast" that ships with Microsoft Office.
There is a downside in using this option on a Windows server that has SQL Server installed, as this service runs continuously and can slow down your server's general performance because it has to index files continuously, as a good practice if you don't need slightly faster file searches, the feature can be safely turned off. Be aware that Indexing Service is turned on by default for all NTFS partitions.
Additionally if you have used FULLTEXT within the SQL Server, I would suggest to test and enable this option on the server where SQL Server is installed. Bear in mind this will have knock-on affect on CPU & Memory usage including the physical disks tuning.
In order to turn this service off to increase overall performance follow these steps:
Open My Computer -> right-click on a Drive icon ->
Select Properties -> Remove the checkmark from "Allow Indexing Service to index this disk for fast file searching" -> Click Apply.
Make sure to select "Apply changes to :\, subfolders and files." before clicking OK in the new window.
Alternatively, you can navigate to: Control Panel -> Administrative Tools -> Services -> Disable Indexing Services.
The main reason to post this blog is over the weekend one of the development server was slow in performing a simple directory search using Windows Explorer, all the times I could see CPU is maxed to 100% which is causing lot of grief to SQL Server services obviously.