Firefox just DISAPPEARED overnight!

Yesterday Firefox was working fine, I just booted up today though to find the shortcut on the desktop had been replaced by an unknown file icon. Strange...so I went to the program folder to open it from there but the ENTIRE program folder has completely disappeared!

I am the only person to have used this computer and I know I did not delete or move the folder or uninstall the program.

What could have caused this? My pc is Virus-free. Is there a way restoring it with all my settings and bookmarks?

I'm a bit concerned because IE7x86 hasn't been working for me for some time so I only have IE7x64 working....for now!

Thank you.

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EDIT: OK, this is just wrong! I just set IE7x64 as my default browser when prompted. Since I no longer have Firefox I thought what the heck, and right before my eyes the Firefox icon restored on the desktop and....IT WORKS! The program folder has magically reappeared too.

Could there be something in SP1 that is forcing users to set IE7 as their default browser? Why should I have to have IE7 set as default just to be able to use a third party browser?

Has anyone else encountered this?

I got this problem yesterday after installing SP1. I have no idea what's going on but it seems like Firefox gets uninstalled on every reboot. The program folder stays but all files in the folder get deleted. I hope this get solved somehow really soon because I wouldn't like to install FF every time I start the computer.

Fyi, I'm running Vista Home Premium 64-bit & AVG anti-virus. The computer is clean of viruses and all other kinds of malware.

Btw, changing the default browser didn't bring back my firefox installation. Also, the mystical disappearing doesn't happen immediately on reboot but after some time. I haven't been able to tell if it is connected to something I do on the computer.

Are there any good programs for Vista that I could use monitor/log disk operations?

While my Firefox folder didn't vanish, the program itself just gave up working after installing SP1. It kept giving me the "Firefox process already running" warning every time I tried to use it. (Firefox 2.0.0.12)

Uninstalling and reinstalling Firefox 2 didn't correct the problem so I gave up and installed Firefox 3 Beta 4 and kept on working. I still haven't found why this happened.

I installed FF 3 beta 5, and it hasn't disappeared yet. Maybe that's because it installs to a different folder, who knows.

I wonder what would happend if I reinstalled Firefox and then modified the permissions for the files that keep disappearing.

What a surprise! I just finished installing SP1 on my machine again (formated earlier this week) and this time Firefox 2 kept working.

This Windows installations in almost pristine as I have very few programs installed. Perhaps on the other one the error was caused by the bloated contents of the Registry or some rearranged entry made during the SP1 install.