I had a problem with INcredimail inserting and making MYSTART my home page and my search toolbar in my firefox browser, since i do not use ie, it did not concern me.
after doing many many unnecessary things I found out how to rid yourself of this.
on the browser
go to tools<options<main type in url or bookmark page you want to use as your homepage and click ok at the bottom...restart browser
on the search bar
click on the left icon on the tool bar, for example firefox default has a G, a drop down menu will come down, click manage my search engines, it will give you a list, highlight MYSTART and delete,click ok,close browser and restart!! Thats it.
hope this is some help and easy to understand.