System Restore is a tool included in Windows since Windows ME. The System Restore tool in Windows ME was not very complex and not very useful. System Restore included with Windows XP is a little more useful, although it is not a full restoration product as it doesn't store every single thing on your computer, it only backs up essential system configuration files. Often it only allows emergency recovery. In Windows Vista and Windows 7 System Restore is vastly improved and far more useful.
System Restore is not a substitute for system or data backup. It's an emergency tool that can be used in the event of a program not installing or uninstalling correctly or a Windows patch that causes problems with an existing installation. It sometimes works for virus and malware infections - but not always.
It can be accessed from Safe Mode or from the Safe Mode startup menu in an emergency situation. It does not always work. Some viruses and other malware can interfere and prevent it working correctly and some malware removes system restore points.
By default, System Restore is turned ON when Windows is installed. It creates a folder called System Volume Information. This folder can become quite big with many restore points held in it so sometimes they should be flushed. It isn't visible in normal usage as it's a protected system file so don't go looking for it.
Windows Vista handles System Restore differently to Windows XP. Where Windows XP only held a limited number of system changes and could only restore what it had saved, Vista has the capability to save many more changes using a feature called Volume Shadow Copy. Volume Shadow Copy basically holds all the system information and many changes to user data files. The Home Basic and Premium Versions have no capacity to use the Volume Shadow Copy system fully, but the enhanced System Restore itself is fully available. Vista Ultimate and Business do have the necessary access to explore and recover data from Previous Versions, a part of the System Restore and Volume Shadow Copy services.
A side effect of the Vista System Restore feature is that it can hold a huge amount of information and many restore points. This includes deleted files, even temporary internet files and files in the Recycle Bin. The system restore file can grow to a huge size on a well used system, particularly in a corporate environment. This is a result of the way the size of the System Restore file is determined. The default size is 15% of hard drive or partition size. If you have multiple Windows partitions, there will a system restore file held for each partition. In the days where an 80GB hard drive was huge, the file was self-limiting as old restore points drop off, but where hard drives are commonly being above 300GB and on many systems above 500GB, the system restore file can become huge. Easily up to 20GB if the the system is left on the default settings for long periods.
To change the default space allowance requires the use of the command line. Unless you are familiar with the use of the command line in any operating system, don't use it. Changes are reversible but, once again, from the command line only.
On Vista Home and Premium, the file should be flushed if hard disk capacity seems to be shrinking. Maybe resized to use a lesser percentage of the total space available.
Some more reading, information and links here
When you have finished, restart the computer and follow the instructions in the next section to turn on System Restore.
Don't do this just to see what happens. It is an emergency tool, not a “suck-it-and-see” utility!!
There are a number of reasons why you might like to consider flushing previous restore points. Holding a huge number of restore points in System Restore can eat up some disk space. Some program installations or removals fail for some reason or another and can affect system files. After a virus or malware infection you don't want to be forced to restore to an “infected” restore point.
Only flush restore points after an infection is completely removed and your computer is clean. Better an infected restore point than no restore point at all.
The safest way is to use the Disk Cleanup tool:
It can also be done through:
For lots more information on System Restore in Windows XP this full tutorial is worth reading:
In Windows ME this utility is not 100% reliable. There have been reports of computers not restarting correctly. So use only as a last resort and only after looking for further information about your problem.