Hi One of your restore points may be corrupted which can prevent other restore points from working.
You may have clear All restore points..and look elsewhere for your system slowing down.
Right click My Computer>properties.
Click on system restore tab.
Select Turn off System Restore>click Apply and restart Pc.
This will delete all restore points.
Once restarted..go back to System Restore tab and deselect Turn off System Restore.
Now click Start menu.
Programs>accessories>system tools>System Restore.
Choose the option Create a restore point.
Enter a description.
Click Create.
You may have clear All restore points..and look elsewhere for your system slowing down.
Right click My Computer>properties.
Click on system restore tab.
Select Turn off System Restore>click Apply and restart Pc.
This will delete all restore points.
Once restarted..go back to System Restore tab and deselect Turn off System Restore.
Now click Start menu.
Programs>accessories>system tools>System Restore.
Choose the option Create a restore point.
Enter a description.
Click Create.