Current control set

The Windows Registry contains the Current control set key:


Current Control Set - Windows 9x/Me

In Windows 9x/Me the Current Control Set key is stored in the SYSTEM.DAT Registry file.

Current Control Set - Windows NT

On Windows NT the Current Control Set key is only present at run-time. The contents of the key is stored in the SYSTEM Registry file and can be determined by reading the Current value from the key:


The Current value contains number of the current control set. Normally 1 or 2 but other values like 3 or 47 are known to be used. For example a value of 1 maps to the Control Set key:


Normally there are multiple Control Set keys the role each of the Control Set keys can be different:

ControlSet001 may be the last control set you booted with, while ControlSet002 could be what is known as the last known good control set, or the control set that last successfully booted Windows.

These roles are defined by the other values in the Select key:

Name Data type Description
Current REG_DWORD Current Control Set
Default REG_DWORD Default Control Set
Failed REG_DWORD Control Set that failed to boot
LastKnownGood REG_DWORD Last known good Control Set


  • Determine if a value of 0 indicates not set

  • Confirm if speculations that 9 is the largest value ControlSet00#