|Have you tried safe mode? Tap f8 on bootup to access it.|
If you can access safe mode with networking then download MCPR.exe to remove McAfee to your desktop.
Also download these other free tools to the desktop
2- tdss killer
4- trojan remover
5- hitman pro.
Now go to msconfig and disable all startup items, click close and then reboot.
a- Once you get into regular mode run the rkill.exe to kill the processes.
b- Now run MCPR.exe to remove McAfee (don't reboot yet)
c- run 2-5 and remove all they find.
Now reboot and see how the PC runs.
If you can't download the above to your PC, do it on another PC, save them to thumbdrive or burn them to a CD and then install them on the problem PC.
You can google for the above, they are easy to find and it will help you in learning how to find things on-line.
Let me know how you make out.
Some HELP in posting on Computing.net plus free progs and instructions Cheers