Ask.com is evil

Somehow, my browser has been altered so that, even though Google is my home page, my default search engine is now Ask.com (mysteriously installed  by iMesh).  I want this crappy search engine off my browser and Google restored as my default, but I cannot for the life of me figure out how to do it.  Can one of you help me?  And could the rest of you form a mob to march on Ask.com and burn their corporate headquarters to the ground?  Thank you!