Ok, lets do a couple of steps here first:

To make sure your windows isn't corrupted because of the power outage, let's run chkdsk.

Click on My Computer, then right click your C: Drive (if you have other hard drives, you will want to run this on them as well). Then, click Properties. Inside that window, go to the Tools tab. Inside that tab, open up the "Check Now" button. That will open a smaller window. Select the checkbox to "Automatically fix file system errors", then hit Start. You will probably receive an error asking if you want to schedule the disk check, click Yes, then restart your computer.

Read http://support.microsoft.com/kb/315265 for more information.

After running the chkdsk, then please go to www.getfirefox.com, and download a fresh version of Firefox. I'm assuming you are using Internet Explorer to download Firefox. Instead of hitting Run, let's try hitting save. Remember where it saves the installer file on your computer.

After the download has finished, double-click and run the Firefox install. Once it is finished, try to start Firefox up. Let me know how it goes!

You may also need to create a new profile, so maybe do that first if the disk check doesn't expose (serious) errors.

Create a new profile as a test to check if your current profile is causing the problems.

See "Basic Troubleshooting: Make a new profile":

• https://support.mozilla.org/kb/Basic+Troubleshooting#w_8-make-a-new-profile

If that new profile works then you can transfer some files from the old profile to that new profile, but be careful not to copy corrupted files.

See:

• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox