Please read: Remember to return and click the Accept button ONLY once your issue is resolved. If the first answer does not work, just REPLY to me and we will continue.
When you get time I would start rooting out software conflicts using my guide below (all steps are reversible)
Trace files left over after uninstall are common. If you want a thorough uninstall of Itunes, you can use an uninstall program like:
Based on what you tried though, I'm betting its an issue with a conflicting program, Virus scanner being the most common. You may have to uninstall your AV to see if its causing a conflict.
Furthermore, for a matter of thoroughness, I'd do a virus scan.
The above is a post infection cleaner, much more thorough than real time scanners. Its called malwarebytes, its free. Do a full scan, if it finds an infection, click Show Results, and click Remove Selected. Restart afterwards.
Lastly, be sure that itunes isn't running in some sort of compatibility switch. Right click the executable, click properties. Check the compatibility tab. Nothing here should be checked.
If you do root out the culprit via msconfig, the vast majority (if not everything) of that can be disabled as its not required for the OS to run effeciently. Almost all programs try to load in startup nowadays.
Anyway, give the above a shot when you get time, and let me know the results. If no improvement, respond using REPLY. Thank you