Do a malware check with some malware scan programs. You need to scan with all programs because each program detects different malware. Make sure that you update each program to get the latest version of the database before doing a scan.

• http://www.malwarebytes.org/mbam.php - Malwarebytes' Anti-Malware
• http://www.superantispyware.com/ - SuperAntispyware
• http://www.microsoft.com/windows/products/winfamily/defender/default.mspx - Windows Defender: Home Page
• http://www.safer-networking.org/en/index.html - Spybot Search & Destroy
• http://www.lavasoft.com/products/ad_aware_free.php - Ad-Aware Free

See also "Spyware on Windows": http://kb.mozillazine.org/Popups_not_blocked and Searches are redirected to another site

• Open the about:config page via the location bar and do a search for mystart via the Filter at the top of the about:config page.
  
• Reset all mystart related prefs that appear bold (user set) via the right-click context menu to their default values.

To open the about:config page, type about:config in the location (address) bar and press the "Enter" key, just like you type the url of a website to open a website.
If you see a warning then you can confirm that you want to access that page.

• Use the Filter bar at to top of the about:config page to locate a preference more easily.
• Preferences that have been modified show as bold (user set).
• Preferences can be reset to the default via the right-click context menu if they are user set
• Preferences can be changed via the right-click context menu: Modify (String or Integer) or Toggle (Boolean)

Start Firefox in Diagnose Firefox issues using Troubleshoot Mode to check if one of the extensions or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox (Tools) > Add-ons > Appearance/Themes).

• Don't make any changes on the Safe mode start window.
• https://support.mozilla.com/kb/Safe+Mode

Cor-el,

Thanks! Your direction worked! MyStart no longer appears when I open Firefox.

I have one remaining concerning, however. Is it possible that my system’s security has been compromised, even though I cannot see MyStart any longer? Could MyStart be accessing sensitive financial information from my pc without my knowledge? I’ve Googled MyStart and Incredibar and could not find anything indicating whether or not they are malware. Do you know?

Don

Mystart.incredibar.com(http://www.Mystart.incredibar.com) is a low quality search web that acts as a web browser hijacker virus to harm computer users. No matter what you type to the search bar of Mystart.incredibar.com, you'll be redirected to a list of links which are helpless at all. Here is the solution to solve such annoying trouble: http://blog.teesupport.com/how-to-remove-mystart-incredibar-com-threat-mystart-incredibar-com-manual-removal-guide/ Good luck.

I do use incredimail...somehow the program got messed up...I re-downloaded and reinstalled it, choosing the "custom installation" feature and unclicking the mystart search engine and home page feature. I've never had the incredimail tool bar, so that wasn't a problem. I now have my chosen home page and everything is working smoothly again...