1866: Acronis OS Selector Fails to Load

Also read in:

use Google Translate

Last update: 23-03-2015

What the issue may be related to and how to overcome it


Acronis OS Selector fails to load with Starting Acronis Loader... or with an endless loop of error messages.

If the error message is MBR Error 3, then the last booted operating system starts.



The most probable cause is that the partition on which Acronis OS Selector was installed has been defragmented. Acronis OS Selector records the absolute address of the following configuration files in the MBR: 

  • bootsect.sys (BOOTWIZ)


  • bootwiz.sys (root directory)
  • bootwiz.cfg (BOOTWIZ)
  • mouse.com (BOOTWIZ)
  • ossmain.exe (BOOTWIZ)
  • parter.exe (BOOTWIZ)
  • x.bin (BOOTWIZ)

(!) If the physical location of these files on the hard drive changes (e.g. during a defragmentation session), then Acronis OS Selector will fail to load.


Reactivate or completely disable Acronis OS Selector using Acronis OS Selector Bootable Rescue Disk.

More information

To avoid the issue in future it is recommended to create a dedicated partition for Acronis OS Selector:

  • Create a small (but not less than 10 MB) FAT/FAT32/NTFS partition on the hard drive. It does not matter if the partition is created at the beginning of the drive or not;
  • Run the Acronis OS Selector installation program (Start -> Programs -> Acronis -> Acronis Disk Director -> Install Acronis OS Selector), uninstall it and reboot. Remember that you should choose the appropriate operating system to boot after the uninstallation (the operating system under which Acronis Disk Director is installed);
  • Run the installation once again in Custom mode and choose the created small partition as the installation path;
  • Reboot the computer and never defragment that partition.