Why does removing threats from some virus scans and some new software require a reboot?

Joseph Videtto January 10, 2013
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I’d just like to have a better understanding of why I’m asked to reboot my computer under different circumstances, so:

1.) Why does cleanning threats detected by a virus scanner often require a reboot? Does that reboot need to be done immediately, or is it ok for me to wait till I’m finished using my computer for the day?

2.) What happens after a program is installed that requires the PC to be rebooted before you can use it? Why is the same reboot required when you uninstall the program? In this day and age, why can’t the install/uninstall procedures do their thing without requiring a reboot?


  1. Luca Vignando
    February 4, 2013 at 10:25 pm

    Sometimes is just a precaution of developers.
    Sometimes instead it is needed: some files cannot actually be installed or updated while the system is running. They are "parked" waiting for the next reboot.
    When this happens, before Windows starts loading most of its stuff those parked files are actually installed. The same happens for uninstall: some files are simply enlisted for removal at next boot and actually cannot be removed until then

  2. Saurav Azad
    January 15, 2013 at 4:42 am

    read the article for more reference http://goo.gl/5dUv

  3. Alan Wade
    January 12, 2013 at 6:12 pm

    Basically, and I do mean Basically, a lot of Viruses, Malware, Scareware etc use system files that under normal operating levels are always in use. Therefore you cannot remove them because of the fact that the infected files are in use.
    By restarting your machine the infected files can be disinfected before they come into use.

  4. susendeep dutta
    January 12, 2013 at 4:06 pm
    • Lisa Santika Onggrid
      January 14, 2013 at 2:04 pm

      Nice read. Thanks.

  5. Anonymous
    January 12, 2013 at 6:10 am

    Cleaning system files or some files which are in use by some other application or by a malware requires reboot. as you antivirus can not delete file while it is in use . so it requires system restart so that it deletes the files before they are being executed at next login.
    This is no compulsory to restart immediately. as your antivirus will control all activity of the file and won't allow it to destroy your system although after saving your files you do need to restart your system.
    Same is the case with installing and uninstalling applications. They need to overwrite some system file there for you need a system restart.

  6. Jim Chambers
    January 11, 2013 at 3:33 am

    Files that are in use cannot be replaced or deleted until the system enters early part of restart sequence.

    • Oron Joffe
      January 11, 2013 at 9:49 am

      Agree, and just to elaborate on that, some files can only be removed during the bootup process since, while the computer is running they are in-use and cannot be removed or altered. Only during the boot up process, *before* that file is called up, can they be deleted safely.
      Some viruses also make changes OUTSIDE the operating system (I think this is what Yiz Borol is referring to) and again, such changes can only be dealt with before the OS has loaded fully. A while ago I encountered such a virus which resided in its own little partition at the end of the disc, and was called by boot loader (the software that calls up Windows when you start up the computer) *before* starting up Windows. Windows was totally unaware of it, and although the AV software could find it, it could only be removed by using a special boot disc which contained the removal software...

  7. ha14
    January 10, 2013 at 10:44 pm

    some does this as precaution

  8. Jan Fritsch
    January 10, 2013 at 8:25 pm

    (2) Actually, for most programs or even drivers the reboot is redundant and not necessary to make them work. This is pretty much a legacy thing some developers or installers haven't got rid off yet.

    (1) It is generally suggested to remove it immediately even if that means closing everything and performing a restart.
    An "active" threat e.g. virus could continue to infect other parts of the files, system or even network while you are working causing more damage then necessary!
    The reason it usually requires a reboot is that those threats usually hide in active background tasks which need to be killed and prevented from restarting.
    Also most cleaning processes take part before the Desktop is loaded because the malware could force a crash of the system to stop your Anti Virus form actually removing them.

    • Yiz Borol
      January 10, 2013 at 10:38 pm

      I'd just like to add to (2): There are some programs(i.e: antivirus programs) that are making high level changes to the OS that require a reboot to be installed, simply because the code can't be changed while it's being used by you.

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