Late April I had a problem with my system that required a system restore. I had four system image backups dating back to December 2010. I tried restoring from the most recent and kept getting errors. The only one that worked was the December 2010 image.
I no longer rely on the Microsoft product, I am now using Acronis True image.
I had good experiences with NtBackup with Windows XP where I had successfully used system restore at least twice so I thought I was on safe ground with the Windows 7 product. Of course NtBackup was not a Microsoft product, poor fool me.