Mystart by Incredibar is a potentially unwanted application which gets installed as an add-on with some other programs like Incredimail. Most of the readers think that it is a virus but it's not. It is a free toolbar like Babylon or Searchqu.
IncrediBar toolbar can be uninstalled just by going to Control Panel and selecting Add/Remove Programs.
How to remove mystart.incredimail.com from IE:
2. Select Search Providers and remove Mystart Search
How to uninstall mystart.incredimail.com from Google Chrome:
2. Select IncrediBar and remove
How to remove mystart.incredimail.com from Mozilla Firefox:
2. Select Extensions. Remove IncrediBar toolbar. Close the window.
4. Remove MyStart Search from the list . Click OK to save changes.