I had a trojan virus attack my computer and after that Firefox would no longer open up. I tried deleting it and re-installing it but that didn't work.
When trying to re-install Firefox, it allows me to download it but when I hit run, it says its extracting and after that nothing else happens.
Wšykne wótegrona (1)
Are you sure the virus is cleaned off your PC?
Download and Install MalwareBytes Anti-Malware, run a full Scan. http://www.malwarebytes.org/
Download and Run TDSSKiller http://support.kaspersky.com/faq/?qid=208283363
Download and Install Microsoft Security Essentials http://windows.microsoft.com/en-US/windows/products/security-essentials (not an official endorsement, but I personally recommend MSE as an awesome permanent anti-virus)
Double check for all Windows Updates.
Then, delete the firefox you downloaded, go to www.getfirefox.com, redownload and try to install Firefox again.