Can't prevent iTunes from starting when I connect my iPhone

Question

I primarily connect my iPhone 4 to an iMac at home, on which pretty much all of my content is stored.  It's set up to sync wirelessly.  Until recently, I synced my calendar and contact data to Outlook on my work computer, which is a PC running Windows XP.  We recently switched to an Exchange server for calendars and contacts, and my backups sync to the cloud, so I don't need to sync anything at work anymore.  I still connect the phone to the computer to charge it and to upload (not sync) photos, but there's no reason to run iTunes, so I unchecked the "Open iTunes when this phone is connected option". 
The problem is that when I connect the phone, it still starts iTunes and goes through a "sync".  I have nothing selected to sync, but it copies "Safari safe browsing data", whatever that is.  When I look, the "Open iTunes ...." box is again checked. If I uncheck it again, the same thing happens again.
My computer's a bit underpowered, so starting a process I don't want to is kind of annoying, and I'd like to stop this.
Any advice would be appreciated.
Thanks,
Eric

Answer 1

Finally figured this out.  I had assumed that the "start iTunes" option was separate for each computer, but apparently, it's a single option.  I had accidentally left it on at home, and since it syncs via WiFi every time I connect it to a charger, this always overwrote what I did at work.  Once I turned it off at home, it stayed off in both places.