I can't believe this thread is still going strong, and people are still suggesting "fixes", thanking each other for them one day, and then saying, "oh, but it doesn't work" the next. The problem is SIMPLE. It is a POOR DESIGN feature of iOS 7 ...
PLUG your iPhone/iPad into the USB of your "trusted" PC while Windows is RUNNING, and you WON'T get the "trust me" message.
PLUG your iPhone/iPad into the USB of your "trusted" PC BEFORE Windows has booted up, or LEAVE PLUGGED IN while Windows reboots after (say) Windows Update - and you WILL get the "trust me" message when the USB port power-cycles.
The TRUST ME message can ONLY be suppressed on a PC that is running iTunes (or possibly other Apple driver software) AT THE TIME YOU PLUG IN.
If your PC is NOT running the Apple software at the moment you connect - YOU WILL GET THE MESSAGE.
APPLE - ALL WE WANT IS THE OPTION TO TURN OFF THIS SO-CALLED "PROTECTION" FEATURE ON OUR IOS DEVICES.
Brian