So what version of Windows 7 do you have and what bit version is it? If your W7 isn't 64bit it will revert back to 32bit firefox browser to have 64bit firefox your O/S must be 64bit O/S.

The OP has 64-bit Windows 7 If you look in more system details.

Are you downloading the stub for Windows from mozilla.org or the full Win64 setup from www.mozilla.org/firefox/all/ ?

WestEnd said

So what version of Windows 7 do you have and what bit version is it? If your W7 isn't 64bit it will revert back to 32bit firefox browser to have 64bit firefox your O/S must be 64bit O/S.

The Windows 7 is 64 bit.

James said

The OP has 64-bit Windows 7 If you look in more system details. Are you downloading the stub for Windows from mozilla.org or the full Win64 setup from www.mozilla.org/firefox/all/ ?

I click the upper right corner update arrow to download the latest version. It took me to this page:https://www.mozilla.org/en-US/firefox/

Thank all for your help!

Did you remove all firefox and deleting any mozilla folder and reinstalling again? This will clear up any firefox that was there before.

WestEnd said

Did you remove all firefox and deleting any mozilla folder and reinstalling again? This will clear up any firefox that was there before.

Thanks for the response. What are you referring to?

If it's the switching from 64 bit to 32 bit. I did as Mozilla support instruction said: installing 64 bit then uninstalling 32 bit. I used the Windows system uninstall to remove the firefox32 , is there any more manual cleaning one should do after that?

As for the recent update to version 63, I installed it on top of the existing firefox64, without uninstalling first. That's what it should be done isn't it? Otherwise you'll lose all your existing bookmarks etc.

leeljc said

James said

Are you downloading the stub for Windows from mozilla.org or the full Win64 setup from www.mozilla.org/firefox/all/ ?

I click the upper right corner update arrow to download the latest version. It took me to this page:https://www.mozilla.org/en-US/firefox/

Hmm, did that give you a choice of 32-bit or 64-bit installers? I thought the only place where you had a choice was:

https://www.mozilla.org/en-US/firefox/all/

I suppose it's possible that if the website or the installer is choosing for you between 32-bit and 64-bit, there might be some reason it would choose 32-bit, but I'm not aware of one.

As of Fx 55.0 Release https://www.mozilla.org/firefox/55.0/releasenotes/

Simplified installation process with a streamlined Windows stub installer. Firefox for Windows 64-bit is now installed by default on 64-bit systems with at least 2GB of RAM. Full installers with advanced installation options are still available

The installer has name"Firefox Installer", can't tell whether it's for 64 bit or 32. Though I clicked on the Windows 64 bit button.

I stopped streamline download because I had big problem with firefox constantly slowing down my computer. At times firefox would freeze up for few seconds while I can see a mini-dump process is running in task manager. Of course this doesn't mean the problem is in firefox, Avast security is also installed and constantly interfering. And I suspect my computer over the years must have accumulated some damages. Anyway that's the reason I switched to manual upgrade.

Thanks all for your help. I'm going to manually switch to 64 bit again and see if the same thing happen again in next upgrade.