Enterprise Software

Get IT Done: Specify the default OS on a dual-boot system to correct a failed install

How to specify the default OS on a dual-boot system


By Ray Geroski

A failed OS upgrade can leave you with a system straddling the fence between the old OS and its intended replacement. You suddenly find yourself working with a dual-boot with one OS failing to load. It's a common headache but one that's relatively easy to fix.

This is just the situation that one user posting in our Technical Q&A forums encountered when attempting to install Windows XP Pro on a problem system. “The new install failed (I forget the details) and left me with a blue screen of death when I tried to reboot,” wrote TopDawg44. Pressing [F8] on startup showed both installations as startup options. TopDawg44 wanted to know how to remove the failed install so he could boot directly into the previous OS without having to press [F8] for the option.

TR members responded to TopDawg44's query and provided two options for getting his system up and running again. You can follow their tips to quickly change a system back to a single boot.

Changing the system boot
One option for removing the dual boot is to edit Boot.ini. “The boot menu is controlled by a hidden file called Boot.ini,” wrote Ericd173. Ericd173 suggested opening the file in Notepad and changing the default option. Because it's a hidden file, you may have to change the folder view in Explorer to make it viewable.

In Boot.ini, the default operating system is specified under the heading [boot loader] with the setting default= as shown in the following example:
[boot loader]
timeout=30
default=scsi(0)disk(0)rdisk(0)partition(1)\winnt


In this case, the default OS the system loads is WinNT. To revert to the previous OS, change the setting specified after default= to the original setting.

You can find additional information on Boot.ini in MSKB article 99743. For additional information on Boot.ini in Windows XP systems, see MSKB article 314081. The article includes details on the purpose of each setting in Boot.ini and how to modify them. If you experience startup problems, this might be a good place to start to resolve the issues.

Member cul8rm8e suggested an alternative for selecting the default boot OS. This member suggested modifying the setting in the System Properties window using these steps:
  1. Right-click My Computer and select Properties.
  2. Click the Advanced tab.
  3. Under Startup And Recovery, click Settings.
  4. Under Default Operating System, the drop-down list displays the current boot system, as shown in Figure A.
  5. Select the original OS from the list.
  6. Deselect the option Time To Display List Of Operating Systems.
  7. Click OK.

Figure A
OS selection in System Properties


The available options may vary depending on the OS you're currently running, but either method offers an effective fix if you encounter the same problem TopDawg44 did. And if you're running a dual-boot system, editing the System Properties settings offers a quick way to change the default OS.

Modifying the default Boot.ini or the System Properties window gives you more control over the boot options you see on startup and can help you get back up and running after a failed upgrade.

Editor's Picks