"System Restore" is built into every copy of Windows XP and ME. In theory, it's sort of a system-level "undo" command that lets you recover from a failed software installation, a software conflict, or other similar problems.

Microsoft describes it this way: "System Restore actively monitors system file changes, so that if something goes wrong with your computer, you can restore your system to a previous state without losing data."

And that's true, as far as it goes. But, if the volume of reader mail I get about System Restore is any indication, many, many users are confused about exactly what System Restore can and cannot do.

System Restore can be useful--and we'll get to the details in a moment--but it's important to note its four main limitations:

1. It doesn't back up your user files and documents. System Restore focuses on system-level files and services; it doesn't back up most files you create. If you munge or permanently delete an important document or spreadsheet, or want to go back to an earlier version of such a document, System Restore can't help you. System Restore doesn't take the place of full, normal backups. (See Fast, Easy Backups For Win98/ME/NT/2K/XP)



2. System Restore isn't a true "roll back" tool. For example, if you install new software that crashes badly, System Restore may be able to get Windows running again, but may not erase the errant program as a whole; may not delete leftover vestiges of the program that failed to uninstall properly; and may not clean up any messes the troublesome program made outside of the system file areas.
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3. The default settings make System Restore an enormous space hog. For reasons known only to the programmers at Microsoft, System Restore, like the Recycle Bin and the Internet Explorer cache, sets aside space for itself based on a percentage of what's available on your hard drive. This might not have been too bad when disks were small, but with today's large hard drives, the total space set aside for System Restore (and Recycle Bin and the IE cache) can be ridiculous: It can amount to gigabytes, in total! This not only consumes disk real estate, but also creates a huge amount of needless extra data you have to process when you do a normal backup.
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4. System Restore is CPU- and disk-intensive when it runs, which is fairly often:
   
   
   • At first boot
   • Every 10 hours of continuous system operation
   • Every 24 hours of real-world time
   • Every time Windows Update installs something
   • Every time you install any software using an installer program that System Restore recognizes (such as InstallShield 6.1 or higher)

If System Restore were a 100% "roll back" or "undo" solution, it might be worth all the activity and disk space. But to me, System Restore takes too much and gives back too little to let it run in its default mode. So, let's look at how you can modify System Restore to make it more efficient, more useful, and far less wasteful. There are three main approaches, and one of them will be right for you:

Simple Option: Let It Run, But Rein It In
You can reduce System Restore's voracious appetite for disk space by manually reducing the area set aside for the Restore cache area. Here's how to access that setting:

In XP: Right click on My Computer, then Properties, and then the System Restore tab. Select the hard drive you wish to adjust (in XP, each drive can have its own System Restore setting), and click the Settings button.

In WinME: Right click My Computer, then select Properties, then Performance/File System/Hard Disk.

Next, in both operating systems, move the slider to choose a reasonable amount of disk space for the System Restore files. I suggest you start by choosing the smallest allowable Restore area (usually a still-hefty 200 megabytes) by moving the slider all the way to the left.

Don't worry: You don't have to guess if that's enough space. Over the next few days and weeks as you use your system, you can check to see if you have enough "Restore Points" available for your own needs and preferences. Here's how:

In XP: Click Start/All Programs/Accessories/System Tools/System Restore.

In WinME: Click Start/Programs/Accessories/System Tools/System Restore.

In both operating systems, select "Restore my computer to an earlier time" and click next. You'll then see a calendar with some dates in bold; those are the days with one or more available Restore Points. Note how far back the bold dates go. Next, click Cancel to exit the Restore tool. (In other words, don't go on to the next step and actually to perform a System Restore; you're just checking to see what Restore Points are available.)

I find that the minimum 200 megabytes of Restore area easily provides a couple weeks' protection for me, but it's highly dependent on how you use your system. If you want to have more Restore Points available, simply repeat the size-setting procedure outlined earlier to increase the amount of disk space available to System Restore until you've found the right balance between disk space usage and the number of available Restore Points.