Do Ii Need Both Microsoft Security Essentials and another AV

hackerman1 said:

i have also not heard about any problems using MSE together with other A/V´s, but when i installed the first MSE beta, i read a note from Microsoft listing some A/V´s that should be uninstalled before installing MSE.
i was using Avira & a2, neither of them was on the list, so i installed MSE, which didn´t complain about them.

I got the same warning. I ignored it and installed anyway. No problems whatsoever...and I was running McFail "Security Center. (It came with the PC).