Finder indexes files withing the drive, and updates the index every time something changes. If you need to turn the indexing off for any reason, this is the code that you will need to put into the terminal window:
sudo launchctl unload -w /System/Library/LaunchDaemons/com.apple.metadata.mds.plist
and your main password.
If you wish to turn the indexing back on:
sudo launchctl load -w /System/Library/LaunchDaemons/com.apple.metadata.mds.plist
and the main password.
Hope this helps.