Can't allocate restore space

I am running Windows 7 Home Premium and am unable to make a restore point because I am told I do not have enough disc space. I have allocated 4% of the 100 GB drive space using the elevated command prompt. The properties pie chart shows I have 57 GB free space. When I use the elevated command prompt to check how much space is being used for shadow copying it shows zero space allocated and zero space being used. I have always been able to make restore points previously without problems. Also when I click on Restore I only have one point to choose from and that was made in February earlier this year.