itunes won't allow automatically open when iphone connects, trying to decrease 'other' storage

I'm on a quest to decrease the 'other' memory being used and came across this tip (http://osxdaily.com/2011/10/18/itunes-other-capacity-taking-up-tons-of-space-fix /) to unclick and reclick the 'open iTunes when this iPhone is connected' box under options in the iphone summary... but it won't let me do anything- it is just disabled for some reason. Please help. Here's a screen shot of my predicament.