Message says Firefox is already running when it isn’t

Last Updated on November 22, 2016 by Dave Farquhar

Earlier this week, when doing an emergency computer upgrade, Firefox gave me a weird problem. I installed Firefox, then when I tried to launch it, I got the popup dialog box stating that Firefox is already running. When, of course, it wasn’t–I’d just installed it.

There are a couple of helpful articles on Mozilla’s knowledge base.  It didn’t quite solve my problem, but it pointed me in the right direction.
I had Firefox installed on the system previously, so I had a profile on the machine. Not much of a profile, but something about it was causing problems. I couldn’t find the profile.lock file in the profile, but deleting the profile entirely cleared up the problem.

So how did it happen?

On this particular machine, I’d been experimenting with Firefox in the past, running it on different drives. At some point, Firefox was on a drive, then that drive didn’t exist anymore. So it could be that Firefox having been present on, say, drive D, and not uninstalled before drive D was removed or wiped or whatever I did, caused some problems. Perhaps something in the old profile–which always resides on drive C unless you take fairly extraordinary measures to move it–pointed to the old installation and got the new installation confused.

Lesson learned: If you’re going to rearrange your drives, uninstall any programs that may be residing on them first.

How’d I find myself reliant on a machine that had such a strange problem? The same way most of my desktop upgrades seem to have gone the last couple of years. I have a box that I’m just messing around with, then something breaks on my main desktop PC that isn’t a quick and simple fix. So the box I’d been using to mess around with gets promoted to regular desktop PC duty. The last time it happened, I wiped the drive and rebuilt it from scratch, but I didn’t really have time to do that this time. It was 7 PM and my wife needed a computer, so I grabbed the machine and hoped for the best. Whether this is a temporary or permanent arrangement just depends on how the next few days go.

The emergency is a power supply that overheats, and it’s a weird form factor, so just driving over to Micro Center and picking up a $30 replacement isn’t a viable option. Newegg has a power supply from a reputable maker–Seasonic–that looks like it may fit, so I’ll investigate that. Or I could transfer the motherboard and hard drive into a standard case and go from there. I have some of those laying around.

But, just to get things working, it was a lot quicker to grab the other machine, set it up, connect and share out the printer, and fix whatever was broken.

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