Is your question then how to restore to last month using System Restore?
Unfortunately, if what you say is true, then AFAIK you are out of luck.
The number of restore points are limited by system settings and
available disk space. If you are low on disk space or low on allocated
System Restore space, the older restore points are automatically deleted
when new ones are created. Or perhaps you turned off System Restore at
some point (that would delete all Restore Points).
In general, restoring to a restore point as old as a month is very
dangerous. If you try to go back that far, you will likely create all
sorts of out-of-synch conditions, and may well make things worse, not
better.
System Restore is a good tool for undoing a *recent* change--for
reverting the operating system to the condition it was in a day or a
few days ago, but that's all it is. I wouldn't try to go back more
than a week, or two weeks at the very most.
