Drive Image is nothing like System Restore, or should that be system restore is nothing like Drive Image. System Restore isn’t a patch on ‘any’ imaging software is it is for a totally different purpose, basically protecting files in system folders and registry settings, etc. it doesn’t protect data files, etc.

System Restore MVP site - http://bertk.mvps.org/
There are many, many reasons why a System Restore may fail. For example, see “Why are previous restore points not working?” in the “Troubleshooting” section of this official Microsoft page:
http://www.microsoft.com/technet/prodtechnol/winxppro/plan/faqsrwxp.mspx