Just a couple of things... I noticed in the screenshot you posted of processes in task manager wasn't elevated to "show processes from all users". If you do that and sort the list by cpu, you will get a fuller picture of what is taking up your cpu time. Remember that 'system idle process' can be at 90% or more at times, and is an indication of whats available, rather that what's in use.
I do see a lot of complaints about McAfee hogging memory and CPU time. It may be something you could consider switching.
You can temporarily disable McAfee's on access scanner to see how much of a problem that's causing, but first you would need to activate the option as follows...
- Click Start, Programs, McAfee, VirusScan Console.
- Double-click Access Protection.
- Deselect Prevent McAfee Services from being stopped.
- Click Apply and OK.
- Exit the VirusScan Console.
NOW you can right click the McAfee icon in the system notification area and click "disable on access scan".
I am not recommending you keep this disabled, I am only suggesting it as a diagnostic check. I usually disable the on access feature of antivirus software in the interest of performance, without issue, but I haven't used McAfee in a few years, so I can't vouch for its effectiveness without it. Also, I don't know your internet or downloading habits.
Remember to go back to the console and reselect 'prevent mcafee services from being stopped" after you re-enable on access scanning. Good luck to you.
Edited by MarkMCS, 17 March 2015 - 01:01 PM.