Depending on your VM ( particularly hyper-v ) you may have a problem where the disk is not correctly picked up after your first install.
If this happens then before your reboot for the first time you will need to edit the file:
/boot/grub/menu.lst
In there you will see references to:
/dev/disk/by-id/xxxxxxx
Remove those and replace them with:
/dev/sda1
That should then resolve you boot up problems.
Here is a video available as well.