Why are you asking in a McAfee Security Forum if it's to do with MSE?
I hope that you aren't running both as that could leave your system wide open to infection.
If MSE is falsely detecting something then I assume they have some mechanism to report it.
I located this page which seems to have links for that: http://www.microsoft.com/security_essentials/support.aspx?mkt=en-us#mainNav
Malwarebytes free version is usually a good one to try in such cases and make sure you update it before running.
Edit: If I misunderstood and you don't actually have MSE installed then sorry about that, but still run the MBAM Free application.
No, for the benefit of other readers I am not running Microsoft Security Essentials ( and I am aware that this is a McAfee forum for McAfee users-after all I have signed up to it)..The trojan flags a screen with a fake MSE message. It has absolutely nothing to do with the security software you are using.
I did add the edit to my post. You'd be amazed at some of the questions we get though.
Did you try running Malwarebytes free?
There is also an excellent removal guide here: http://www.bleepingcomputer.com/virus-removal/remove-fake-microsoft-security-ess entials-alert
Scroll down the page as those links you see at first are all adverts.
Thank you for the final link. It is spot on and very clearly written. I am going to give it a try.
OK, good luck. That forum is an excellent source of knowledge.