I have seen mention in several postings of a program called "Go Back" which as the name suggests would restore your computer to an earlier time. From my experience System Restore will not restore your computer to any point where there is an unhealthy environment. It will only restore to a healthy system point.
Here is what Microsoft have to say about System Restore.
Troubleshooting System Restore in Windows XP
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The information in this article applies to:
Microsoft Windows XP Home Edition
Microsoft Windows XP Professional
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SUMMARY
This article describes how to perform basic troubleshooting for issues that involve the System Restore tool in Windows XP.
MORE INFORMATION
To troubleshoot System Restore issues, try one or more of the following steps:
If you receive an error message that is related to System Restore, always make sure that you first record the error message and follow the instructions that the error message contains to try to resolve the issue. Most System Restore issues generate an error message that contains a description of the issue and suggestions for how to resolve the issue.
Make sure that you have enough disk space on all of the drives on which System Restore is enabled.
Make sure that the System Restore service is running by using one of the following methods:
Check in Control Panel:
Click Start, click Control Panel, and then click Performance and Maintenance.
Click Administrative Tools, click Computer Management, and then click Services and Applications.
Click Services, and then click System Restore Services.
Open a command prompt window:
Click Start, click Run, and then type CMD.
Press the ENTER key, and then type Net Start at the command prompt to make sure that the System Restore service is up and running.
Make sure that System Restore is enabled on the drives that you want System Restore enabled on.
Try to run System Restore in Safe mode.
If you suspect that you do not have as many restore points as you should have, make sure that the data store is the size that you want the data store to be.
Check the event logs to investigate System Restore service errors:
Click Start, click Control Panel, and then click Performance and Maintenance.
Click Administrative Tools, click Computer Management, double-click Event Viewer, and then click System.
Click the Source tab to sort by name, and then look for "sr" or "srservice." Double-click each of these services, and then evaluate the event description for any indication of the cause of the problem.
For additional information, see the article numbers below in the Microsoft Knowledge Base:
Q287505 How the System Restore Utility Uses Drive Letters
Q283073 How to Disable the System Restore Configuration User Interface
Q295050 Information on System Restore and Password Restoration
Q283252 Non-Administrator User Is Unable to Start System Restore Utility