firefox not responding?

[Fred]

Obviously some program on your machine thinks Firefox is your default browser and is trying to start it. And of course it will not respond if it is not there. Have you ever had it installed? If so your uninstall has not completed properly. You may need to reinstall and then uninstall correctly afterwards. You could try a registry clean using ccleaner.exe from http://piriform.com.
Alternatively you may have malware which is continuously trying to open Firefox, so you should first do a malware scan.