Hi there and welcome
On your computer, can you go to control panel, Programs n Features > highlight QUICKTIME and click CHANGE then REPAIR.
Then once done, restart the computer and tell me if it now works
ok, can you click on my link below and download and install itunes again
Download and run the installation and once done, restart and tell me if the phone now connects please
ok, let me know how it now goes please
ok, which anti virus software do you use?
ok, can you disable it until next reboot, then try iTunes please.
ok, butt if you run the diagnostics, you get the error still?
when did it last work on this computer?
ok, I want to do a system restore please.
To do this, close all programs.
Press the windows key + X and click on Control Panel
click System and Security
Then click on System
Then System Protection
Then System restore
Choose a date before this problem occurred.
Let it complete and tell me if it now functions correctly please
ok, we need to do a full reinstall of iTunes then
Click start, control panel, programs, uninstall a program
Uninstall the below software in the following order. Then, restart your computer.
Apple Software Update
Apple Mobile Device Support
Apple Application Support (iTunes 9 or later)
Once you have restarted, install iTunes again from my link below
Once done, try it again
Let me know the results please
thats the exact error it now gives?