Directory service restore mode is also a safe mode after startup. According to Microsoft's instructions, it is specifically for domain controller recovery, so it can be regarded as a special safe mode. This mode seems to be of little use for ordinary computers and is not applicable to desktop systems (such as XP/V/7, etc.). However, its use is not limited to just domain controller recovery.
Once I was installing Office 2007 under XP, and soon after the installation started, it prompted "The installer cannot update one or more protected Windows files". I tried it many times and it was like this. I thought it must be the Windows file protection mechanism at work, so I booted into safe mode. When I installed again, I found that Windows Installer didn't run in safe mode, and Office 2007 couldn't be installed. Looking at the F8 menu, I suddenly found that I hadn't used "directory service restore mode" much. I tried to enter it to install Office 2007, and unexpectedly it succeeded. Then I realized that most services and system processes run in this mode, but the system file protection doesn't run. If you encounter similar problems, you can try directory service restore mode, and maybe there will be a surprise. However, ADSL can't dial up in directory service restore mode either!
Once I was installing Office 2007 under XP, and soon after the installation started, it prompted "The installer cannot update one or more protected Windows files". I tried it many times and it was like this. I thought it must be the Windows file protection mechanism at work, so I booted into safe mode. When I installed again, I found that Windows Installer didn't run in safe mode, and Office 2007 couldn't be installed. Looking at the F8 menu, I suddenly found that I hadn't used "directory service restore mode" much. I tried to enter it to install Office 2007, and unexpectedly it succeeded. Then I realized that most services and system processes run in this mode, but the system file protection doesn't run. If you encounter similar problems, you can try directory service restore mode, and maybe there will be a surprise. However, ADSL can't dial up in directory service restore mode either!