The registry stores System Restore keys and values in three places. You can change registry values to configure System Restore, but I strongly recommend that you use the utility's UI to make changes whenever possible. Changing registry values can destabilize a system, so be careful.

The three registry subkeys are

  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Sr
  • HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SrService
  • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SystemRestore

The first subkey controls System Restore's filter*don't alter this subkey in any way. The second subkey controls the System Restore service, and you shouldn't alter it in any way either. If you change either of these subkeys, you'll likely disrupt the functioning of your system.

The third subkey includes some values that you can change. You can increase the DiskPercent value to make more room available to store restore points. The default value is 12 percent of your hard disk, although the actual size might vary. For hard disks smaller than 4GB, the actual value is 400MB. You can also decrease this value if you have a hard disk larger than 4GB and don't want to give 12 percent of it to System Restore. To use the System Restore UI to change this setting, run the Control Panel System applet, select the System Restore tab, select a hard disk from the list of available drives, click Settings, and adjust the Disk space to use slider.

You can change the RPGlobalInterval value to specify the interval between System Restore's automatic creation of restore points. For example, to change the interval from every 24 hours to once a week, change the default value of 86,400 seconds to 604,800.

If for security reasons you don't want to save restore points for long periods, you can change the RPLifeInterval value. The default value is 7,776,000 seconds, or 90 days. To change the interval to 2 weeks, set the value to 1,209,600.

Again, don't change a value if you're not sure that it's safe to do so. See the Microsoft article "The Registry Keys and Values for the System Restore Utility" (http://support.microsoft.com/default.aspx?scid=kb;en-us;q295659) to learn more about which values are safe to alter.