I understand your concern, however the information you posted is incorrect (cookies are used by IncrediMail to recognize your installation in order to allow you to download from the IncrediMail Gallery). This does not refer to MyStart, which is a webpage, and is not an installation. Therefore, there is no way to 'uninstall' it.
Please note the information you found can be posted by any user, and is not necessarily correct or updated. In addition, IncrediMail does not and has never included Spyware, Addware, or anything similar, and is constantly checked and approved by the top Download sites and AntiVirus programs available:http://www.incredimail.com/english/incredimail/safe-and-free-incredimail-download.aspx
Please follow the instructions I sent, and let me know if they worked. If not, I can check to see exactly what happened and help you correct this.