Hello, Please try launching Firefox in [[Troubleshoot Firefox issues using Safe Mode|Safe Mode]] to see if that helps. If you can't open Firefox at all then holding down the shift key while opening Firefox will put it into Safe Mode. If Firefox works fine in Safe Mode then it is most likely an add-on that is causing the issue. Follow the instructions in the article linked above to troubleshoot the issue. If Firefox still doesn't work in Safe Mode then it may be a virus / malware issue. You can try these free programs to scan for malware, which work with your existing antivirus software: * [http://www.microsoft.com/security/scanner/default.aspx Microsoft Safety Scanner] * [http://www.malwarebytes.org/products/malwarebytes_free/ MalwareBytes' Anti-Malware] * [http://support.kaspersky.com/faq/?qid=208283363 TDSSKiller - AntiRootkit Utility] * [http://www.surfright.nl/en/hitmanpro/ Hitman Pro] * [http://www.eset.com/us/online-scanner/ ESET Online Scanner] Further information can be found in the [[Troubleshoot Firefox issues caused by malware]] article. I hope that helps. Let me know if not.