Hi upsfeup,

This usually happens when the installer needs to copy/modify files that are currently in use. There is a "Pending" feature in Windows that allows an installer to specify that a task to modify a file happens after a reboot, and before everything else in Windows has started up.

I know it can be inconvenient, but there really is a reason for it :)

Hopefully this answers your question!

I understand that, my question is more specific: what file could possibly be in use since Firefox was not running and hence could be replaced.

If Firefox needs to change more files than the ones that it brings, then its cumbersome to the user and it usually brings more harm than good as it can break something else in the computer.

I'm updating the browser, not anything else.

I am wondering the same. In former times Firefox never needed a reboot, and it does not make any sense because no Firefox-related file should be in use at the time of uninstallation. (Forget about updating in my case; I am doing a clean uninstall, and Firefox insists in rebooting anyway.)

Windows reboots due to software uninstallations are generally only required in the following cases:

• If files that belong to Windows are being modified. I hope Firefox does no such thing...
• Part of the software being uninstalled is still running, so that its files are in use. However, I completely closed Firefox and even used the task manager to make sure no firefox-related processes were running.

Some applications (i.e. Adobe Reader) install fancy "Speed Launchers" that are loaded at boot time and stay resident in memory. Unless these processes are manually killed before uninstallation, they may also be the reason why a reboot is necessary. However, Firefox should not do such a thing.

To summarize it, the question is: Which part of Firefox is running during uninstallation so that removal of the corresponding files is required?

Generally, I consider this a very bad software behavior, one that I would expect from some commercial software producer who wants to install his speedlaunch or logging stuff on my computer, but not from a free project like this one.

Firefox Portable does not do this, easily proving that technically it is not necessary. Earlier versions of Firefox also refrained from doing such a thing.