Hi,
I guess the infection what you have in your computer must be severe that’s the reason; McAfee was unable to clean or delete it from the computer.
Moreover, rebooting the computer in Safe Mode is very simple; all you have to do is turn off the computer completely. Restart it back, and the moment you restart the computer keep on tapping the F8 key on the keyboard until you get a Windows Advanced Option on the screen.
Once you are able to see that (by using your up/down arrow key on the keyboard) select Safe Mode with Networking and hit Enter twice and that would help you to boot up the computer in Safe Mode
You can also try to restore your computer to an earlier date to check and whether we are able to fix it. In order to try that, after you login to the computer in Safe Mode – You will get a window which says Windows is running in Safe Mode… So please click on NO that will bring up the System Restore Window.
Select a date on which the computer was working fine, complete the restore process and reboot the computer; if you are able to complete the restore process successfully everything should work fine

happy