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When I tried to install Internet Explorer 9 on my development machine I got a dialog box stating that I need to close some programs during install. It also says that these programs use files that needs to be updated.

Here is the list:

  • Firefox
  • Java(TM) Update Scheduler
  • Microsoft Visual Studio 2010
  • OfficeScan NT RealTime Scan
  • Windows Desktop Gadgets
  • Windows Explorer

I can accept that MS want to update files that are part of the operating system or other programs from MS. But what do they want do do with Firefox for example. ...and why should I disable or close my Virus scanner at any time at all.

What changes do MS do to Firefox? This really annoys me because they should do anything to Firefox, its a holy principle.

I canceled the installation for now, hope to get some insights first!

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up vote 6 down vote accepted

Windows uses a file locking model in which a file cannot be modified in any way if another program has that file open. This is why you often need to close other programs when installing software on Windows and to reboot the machine after doing some updates. (It needs to replace files which are being held open by Windows itself, so Windows needs to be shut down to complete the process.)

In this case, it is very unlikely that Microsoft is modifying any files which were installed by Firefox. Firefox uses a number of system libraries which come from Microsoft and, apparently, one or more of those were among the files that the MSIE9 install needed to replace.

As for the anti-virus software, one of the things that it does as part of its normal operation is to monitor system files to ensure that no malware modifies them. Depending on how your particular AV software operates, it may hold those files open, which (again) would prevent them from being replaced. Even if it doesn't, it would see that another process (the MISE9 installer) had changed them and then complain very loudly that your system had been compromised. It might also revert them to the previous version in an attempt to undo the "attack" which changed them. Either way, this would interfere with the MSIE upgrade process, so the AV needs to be shut down first.

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I accept most of this answer as it seems reasonable it would work this way. What I can't accept is the disabling of AV-software on a windows machine... Didn't think MS would express themselves like this, if they have to why not update/replace files on reboot, and do i quietly. – Anders Mar 16 '11 at 13:03
"if they have to why not update/replace files on reboot, and do i quietly." This is how Windows Update usually works, but IE tries to do it without a reboot. – Powerlord Mar 16 '11 at 21:40
The more I think about it the main issue here is that they want to turn of anti-virus which is a major security breach. – Anders Mar 17 '11 at 7:01

IE9 installation was designed to be installed without the typical Windows reboot normally associated with software installations.

As indicated in this MSFT employee blog - "The Internet Explorer 9 Setup program will attempt to close programs that are using IE binaries before installing the updated versions." (Source)

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Great that you pointed out this article, explains some of this! – Anders Mar 16 '11 at 13:10

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