Download and save the Firefox installer to the desktop and start the installation with a double-click on the desktop icon.

You can find the full version of the latest Firefox 25.0.1 release in all languages and for all Operating Systems here:

• http://www.mozilla.org/en-US/firefox/all.html

It is possible that anti-virus software is corrupting downloaded files or is interfering otherwise.

Try to disable the real-time (live) scanning of files in your anti-virus software temporarily to see if that makes downloading and installing work.

See:

• http://kb.mozillazine.org/Unable_to_save_or_download_files

browser.download.manager.scanWhenDone

Have you restarted Windows since this problem started? Sometimes the Windows installer accumulates too great a backlog of deferred updates and stops working correctly, giving random errors. Shutting down and restarting Windows completes those installs and usually clears up that problem.

I also would check for malware possibly corrupting or blocking the install. As a supplement to your regular security software, you could try the (free) scanning tools listed in this support article: Troubleshoot Firefox issues caused by malware.

Thanks for the quick reply. Unfortunately, neither of those two solutions has worked - the full installer gives me the "file is corrupt" error message when I save it to my desktop and then run it, just like it does when I simply run it from the page.

As for the other suggestions in that bottom link you gave me, do you find any of those suggestions in particular to be more likely solutions than the others?

Yes, jscher2000, I did try restarting it more than once, which hasn't done anything yet. Would it make any difference if i turned it off/on rather than a normal restart?

I've used at least 4 malware detecting programs so far and have found many threats, but have cleaned those and restarted, and seen no improvement in FF's installation issues so far.

I'll keep trying other ones suggested on that page you linked to for the moment. Thanks!

Try the FTP server:

• https://ftp.mozilla.org/pub/mozilla.org/firefox/releases/latest/win32/

You can also try to download Firefox via FTP:

• [/questions/964240] How do I install Firefox on a computer with no current browser on it?

Open a cmd.exe command line window and execute these commands:

ftp
open ftp.mozilla.org
username: anonymous
password: anonymous
cd pub/mozilla.org/firefox/releases/latest/win32/en-US
ls
binary
lcd x:\ (drive letter of the USB drive or use a folder on the c drive)
get "Firefox Setup 25.0.1.exe"
(check that you have the Firefox Setup 25.0.1.exe file on the USB drive)
bye

Thanks for this! I tried the first US English version on the ftp site, which I noticed did NOT have "stub" in the filename, unlike all the ones I'd been trying. I have no idea how much longer I"ll have to scan for malware just for the sake of safety, but Ff is at least running again and has all my old settings/bookmarks. Thanks again. I'll try and remember all of these tips in the future.

You're welcome