EFI, GPT, BIOS ..GRUB issues

[stepper]

Didn't know where to put this..under Windows or Linux subforums, but anyway.

I have the ACER 257m laptop came with Windows 7 Pro installed. So I installed Archlinux on it to dual boot with Windows.

After install, reboot but no GRUB menu... I googled for solutions which mostly suggested that I install grub-efi, efimgr since Windows boots in UEFI as stated by the C:\Windows\Panther\setupact.log file and also change boot mode to UEFI in BIOS settings .

I installed grub-efi and GRUB works, I can boot Arch but not Windows in UEFI mode. Windows only boots in Legacy mode.
How is this possible?
How can I get both Windows and Arch in one GRUB menu and both boot correctly without changing the boot mode in BIOS?

 

[ginggs]

I installed grub-efi and GRUB works, I can boot Arch but not Windows in UEFI mode. Windows only boots in Legacy mode.
How is this possible?

Maybe your Windows was installed in Legacy mode.

Either install both OSes in UEFI mode, or both OSes in Legacy mode.

 

[stepper]

This laptop came with factory installed Window 8.1 and embed product key in BIOS. Acer SA downgraded to Windows 7 but didn't provide the product key they used so couldn't activate Windows 7, then formatted and installed Windows 8 and Arch in UEFI. GRUB boots both OSes ok...thanks.