Hair Problem on Head

Hi everyone, I’m new to using Blender and I have just finished designing my first 3d head. But I have a problem with the hair system which does not work out what I wanted. So hopefully someone here can kindly tell me what to do.

I design half of the head and then using the mirror modifier and to create the whole head with subsurf on. But when I use the hair particle, it just show only on the mirrored side of the head(hair on 1-side). I tried to use the particle mode which have the mirror function but it still dont work. I have tried using google to find a solution but cant find 1…hopefully I can find my solution here…:o

Here is a picture of my 3d head with the one sided hair…

1)Apply mirror modifier
2)go in weight paint mode and paint the area u want
3)in particles system in extras tab down there is vertex group, pres tri at neg button & select your group.
Sorry for my english. Hope it helped.