I did something similar to this once:
Find out how much your company is paying for McAfee protection services. This might take a little finesse, maybe find the person that knows and take 'em out for a drink.
Since it's a company computer, reach out to other anti-Virus vendors and have them make a sales call to your company.
Information Technology departments are generally under-funded and dollar driven , so if you can figure out how much McAfee is gouging your employer, let the competition know the ball park so they can compete for your employer's business. Obviously this might approach the limits of ethical behavior, but sometimes you just gotta do something to get the ball rolling. For me, it worked and I know for a fact no sales staff lost a job over it.
-Jon