The total size a VHD file is determined at the time you create it. If you want to increase the total size of the VHD file, you would have to do it just like with any real hard drive, first increase the size of the partition and then expand it.

• First use VHD Resizer to increase the file.
• Then map the new VHD as a second hard drive to the old vm.
• The last, go to DOS command.
  
diskpart
list disk
select disk=1
list partition
select partition =1
extend