This question is similar to the answer of Dual-boot Ubuntu 12.10 on UEFI along Windows 8 (GRUB - error: can't find command drivemap), but Windows 8 is installed on a legacy partitioned drive.
What steps need to be performed to make the installation boot in UEFI mode without converting to GPT or using DISM?
I know that it is generally not recommended to mix UEFI and legacy booting, but it can be handy in some setups.