do you really have the administrator previledge?? my suggestion is remove firefox and all its addons, do a reboot of your pc, and go mozilla official download a completely new install pack of firefox 3.6.16, do some test to see if it can work, if don't try ie 7/8/9 or google chrome 10.x, if firefox 3.6.16 can work properly, download a completely new install pack from mozilla official to install a new firefox 4 and do some test to see if it can work as your own wish there.

You're not reading what I'm telling you. Uninstall won't remove v4 because it says the install has yet to be completed ... but the install can't complete because the program keeps asking for a reboot ... but half a dozen reboots haven't changed anything.

All I can think of now is to go behind the curtain and delete everything that says Mozilla or Firefox manually ... but that is always dicey and I don't exactly know what I'm looking for.

I desperately need to get browser function back and hope you have another approach that won't require scrubbing my C drive and reinstalling everything all over again.

i have encountered 2 reasons for this. 1st. wrongly uninstalling firefox 3.6.x, for instance, if you remove 3.6.16 through control panel, but you did not reboot your OS, then you make the installation of the new firefox 4.0. then it all messed up like that, you have to do a instant reboot of your pc after uninstall of your 3.6.16, then after then restarting of your windows, then do a new install of the firefox 4.0. 2nd, not having enough admin privilege, but have partial privilege for that. ok. check yourself.

Nowhere in the process did the website tell me to do anything other than install v4 to upgrade my 3.6.x. In retrospect, perhaps I should have uninstalled one before installing the other, but what I should/could have done to avoid the problem is irrelevant at this point.

I have the problem. Firefox 3.6.x is gone and Firefox 4 is hung up in limbo. In this state, I can't re-install 3.6.x and I can't uninstall 4. I need a solution that will get me out of the situation I'm in right now.

If I can't go into the registry and essentially do a manual uninstall, about all I can think of is to scrub the C drive and re-install every program on the computer. That is more than I even want to think about.

How would I do a manual uninstall?

Please do the following because I suspect FF is running in the background still.

Hit CTRL+SHIFT+ESC to launch Windows Task Manager, then go to the Processes tab and look for firefox.exe. If you find it, right click it and choose Kill Process.

Then go to Download Firefox 4.0 and download a fresh installation file to the desktop. If necessary, download the file with IE8 or 9 and choose to save it to your desktop when you see the prompt.

Then go to Add/Remove Programs, scroll down to Mozilla Firefox and remove it, choosing to keep your bookmarks, customizations etc., (don't checkmark the box).

Then reboot and delete the folder called Mozilla Firefox at this location: C:\Program Files\Mozilla Firefox

Finally run the installation file you downloaded to the desktop earlier.

If I can get v4 out of there, I am tempted to just re-install 3.6.16 and call that good enough. I am out of town at the moment but will try your solution when I get back tomorrow. Wish me luck.

If you want to revert to 3.6.16, you can download it from: Download Firefox v3.6.16

The uninstall/reinstall procedure is the same in either case.

There is no Firefox in the Processes list and I still get a reboot message when I try to uninstall v4. What now?

Please go to C:\Program Files\Mozilla Firefox\uninstall and run helper.exe | Next | Uninstall

No good. I still get the same message that I have to reboot to finish the install. When I do, I still get that message. All I can think of is a manual install ... but let's come up with SOMETHING! This is becoming another career!

There's a comprehensive guide over @ http://kb.mozillazine.org/Uninstalling_firefox which might help.

I wish somebody had suggested that four days ago. It seems that v4 is finally gone. I am happily back to v.3.6.16 ... and will stay here!

OK. Sorry it took so long.

At least we got it done.