I went through this with a friends computer a few weeks ago. I wanted to uninstall the old McAfee so I could install a newer version. The old version didn't even show up in the "add remove programs" area. I tried everything.
How I got rid of it was to contact McAfee and talk to a tech online. He gave me the instructions to get rid of the old program. What it consisted of was going into the registry and following his careful instructions, (which I printed out) removing anything that anything to do with McAfee. It took a while but it worked perfectly.
Whatever you do, don't just go in and try this without the instructions as you could really screw up your computer.
BTW, The new McAfee program I installed shows up in the "Add remove Program" section and could easily be removed. Good luck