Use a full version to install Windows 8 instead of an upgrade version. Upgrade versions will not install properly because the 64GB flash drive can only allocate 34GB of space for a Windows partition which is not enough free space to accommodate an upgrade installation.
To install the full version of Windows 8:
- Back up your data from the Windows partition.
- From the Go menu, select Utilities
- Double click on Boot Camp Assistant
- Click Continue, then place a checkmark next to "Remove Windows 7 or later version" to delete the existing Windows 7 partition. Warning: This will erase your existing Windows 7 partition. Be sure you have a backup before proceeding with this step.
- Use the Boot Camp Assistant to install a full version of Windows 8.
- Once installation completes, restore your data from your backup.