The Registry Keys and Values for the System Restore Utility

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry

In the registry, you can modify many values for System Restore. However, it is recommended that you use the user interface whenever possible to configure System Restore, as you may be unable to reverse the changes you made in the registry, which can place your computer into an unstable condition.

In Windows XP, there are three registry keys that you can use to modify System Restore:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Sr
This key is related to the System Restore filter. This key and its values must not be be modified under any circumstances as any modifications can cause the operating system to malfunction.

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Srservice
This key is related to the System Restore service. This key and its values must not be be modified under any circumstances as any modifications can cause the operating system to malfunction.

HKEY_LOCAL_MACHINE\Software\Microsoft\WindowsNT\CurrentVersion\SystemRestore
In this registry key, you can modify some DWORD values. However, in this key, there are some values that must not be modified under any circumstances.

Values That Can Be Modified Without Risk of Harm to the Computer
CompressionBurst
This value, listed in seconds, specifies the idle time compression: The amount of time to compress data after the computer reaches its idle time. A service can compress data for the amount of time that is specified in this value, and then stop. Then, at the next idle time compression, the computer can repeat the process.

DiskPercent
This value relates to the percentage of disk space that System Restore uses for its data store. The default value is 12 percent. The data store size is always calculated as "max(12 percent, DSMax)," regardless of the size of the hard disk. The maximum (max) size is what is specified in DSMax. For hard disk sizes that are less than 4 gigabytes (GB) in size, 12 percent is less than 400 megabytes (MB), so "max(12 percent, DSMax) equals 400 MB." For hard disk sizes that are greater than 4 GB, 12 percent is greater than 400 MB, so "max(12 percent, DSMax) equals 12 percent." This data store size is not a reserved disk space, and the data store size is used only on demand.

DSMax
This value specifies the maximum size for the System Restore data store. The default size of the data store is 400 MB. The data store size is always calculated as "max(12 percent, DSMax)," regardless of the size of the hard disk. The maximum (max) size is what is specified in DSMax. For hard disk sizes that are less than 4 GB, 12 percent is less than 400 MB, so "max(12 percent, DSMax) equals 400 MB." For hard disk sizes that are greater than 4 GB, 12 percent is greater than 400 MB, so "max(12 percent, DSMax) equals 12 percent." This data store size is not a reserved disk space, and the data store size is used only on demand.

DSMin
This value relates to the minimum amount of free disk space that System Restore needs so that it can function during the installation process. Also, this value relates to the minimum amount of free disk space that is needed for System Restore to reactivate and to resume the creation of restore points after System Restore has been disabled because of low disk space.

RestoreStatus
This value specifies if the last restore operation failed (0), succeeded (1), or had been interrupted (2).

RPGlobalInterval
This value specifies, in seconds, the amount of time that System Restore waits before it creates the automatic computer check points for elapsed time. The default value is 24 hours.

RPLifeInterval
This value specifies, in seconds, the restore points Time to Live (TTL). When a restore point reaches this time and it is still on the system, it gets deleted. The default value is (7776000), which will be 90 days.

RPSessionInterval
This value specifies, in seconds, the amount of time that System Restore waits before it creates the automatic computer check points for session time (the amount of time that the computer has been on). The default value is zero (0), which means that this feature is turned off.

ThawInterval
This value specifies, in seconds, the amount of time that System Restore waits before it activates itself from a disabled state (after the conditions for this process to occur have been met). If you start the System Restore user interface, System Restore is activated immediately.

Values That Must Not Be Modified
CreateFirstRunRp
This value instructs the computer to create the first restore point, for example, when System Restore is turned off, and then turned back on, or disabled, and then activated. This value must not be modified under any circumstances as a modification can place the computer in an unrecoverable situation (for example, the computer is unable to create a first restore point in any of the preceding situations).

DisableSR
This value turns System Restore either on or off. If you turn System Restore off in the registry, the existing restore points are not removed. This value must not be modified. System Restore must be turned either on or off only from the user interface.

RestoreDiskSpaceError
This value instructs the computer to produce an error message in case System Restore is unsuccessful because of problems related to disk space. This value functions as an informational value.

RestoreSafeModeStatus
This value specifies if the last restore operation had been performed from the Safe mode.

TimerInterval
This value is the pulling time specified in seconds. This value relates to the time that System Restore "wakes up" and checks for the condition of its disk space. The default value is 120, and it must not be modified as any modifications can affect overall computer performance.

APPLIES TO: Microsoft Windows XP Home Edition, Professional