Yesterday, I used the shredder and I had to restart the computer because there were files that could not be deleted or in use. This was the second time I had to this. The first was a few years ago when I had a virus that messed up my internet explore. I have noticed since the installation of the windows 10 the virus scan runs very slow especially when I am on the internet .
Moved this to Quickclean and Shredder as a better spot for it.
It's not unusual to have to restart in order to delete some files, but I would be careful how you use Shredder
Tools like that are good if you know exactly what you are doing.
Regarding the slowness, that's possibly due to corruption cause by the upgrading to Windows 10.
I would do the following:
Uninstall all McAfee via Control Panel > Programs and Features
Run the MCPR cleanup tool and reboot.
Reinstall your software form your online account.