The link you gave me about Vista states the following:
System Restore helps you restore your computer's system files to an earlier point in time. It's a way to undo system changes to your computer without affecting your personal files, such as e‑mail, documents, or photos.
Sometimes, the installation of a program or a driver can cause an unexpected change to your computer or cause Windows to behave unpredictably. Usually, uninstalling the program or driver corrects the problem. If uninstalling does not fix the problem, you can try restoring your computer's system to an earlier date when everything worked correctly.
System Restore uses a feature called System Protection to regularly create and save restore points on your computer. These restore points contain information about registry settings and other system information that Windows uses. You can also create restore points manually.
My concern is if I were to get some malicious software that were to destroy and infect some of my files in the Windows Registry would a System Restore overwrite these infected files if the System Restore was done when the Windows Registry was free of malicious software?