Please make sure you have fully updated Windows XP (installed all Service Packs, all updates, all hotfixes). Then try downloading again from www.getfirefox.com and let us know if you still get an error

Windows XP SP3 with all fix (tested yesterday). Try with a new downloaded 35.0 exe: same crash. Try with a new downloaded version 34.0.5 exe: all OK.

Have you turned off the Windows XP Firewall? There is a bug that can be caused by the Firewall service being stopped.

Alternatively, if you update from inside Firefox (using the instructions at Update Firefox to the latest release) rather than using an installer, does that work?

Reinstalled 34.0.5 from .exe: ok Checking for new version and update: ok Click on restart button to run new version: helper.exe crash but new version starts and works.

NOTE: when setup of 35.0 crashed, I can run firefox, it is in version 35.0 and all seem working well.

The crash of the 35 installer is caused because your Firewall is turned off.

Why 35.0 crash and 34.0.5 does not? I'm behind a Company Firewall and the single machine does not need a local firewall.

And: is Windows Firewall part of Firefox?

We're sorry to hear that your Firefox seems to be crashing when you open it. Please perform the following steps to give us a crash report ID that helps us find out more about the cause of the crash.

1. On the keyboard, press [Windows] The image "Windows key" does not exist. + [R]. This should bring up a Run window that contains a text field.
2. In that text field, type %APPDATA% and press Enter. An explorer window should open.
3. From that explorer window, double-click on the Mozilla folder, then double-click on Firefox and then on Crash reports. Double-click on submitted.
4. Now, you should see a list of files that contain reports. Go to View > Arrange Icons by > Modified to get the most recent files at the top of the window.
5. Open the most recent 5 files with a text editor and copy the IDs.
6. Paste each ID with bp- into the reply window on the forums.

Thanks in advance!

You can find more information and troubleshooting steps in the Troubleshoot Firefox crashes (closing or quitting unexpectedly) article.

There is a bug in the Firefox 35 installer that causes it to crash if XP's firewall is turned off. We've identified it and fixed it for future versions.

and no, Window's Firewall isn't part of Firefox

Thanks!Tyler Downer said

There is a bug in the Firefox 35 installer that causes it to crash if XP's firewall is turned off. We've identified it and fixed it for future versions. and no, Window's Firewall isn't part of Firefox

THIS is THE answer!

-)

Thanks!