After openSUSE 13.1 installation next to Windows 7 (on a second hard disk) only Windows can boot

Hi,
it is been a very long while since i did a dual boot installation of openSUSE, but today i had to do it on a Windows 7 pc.
At first i will give you the specifications:
- Windows 7 (64 bit) was installed on a 3TB hdd (EFI boot is selected in the bios, i do not know but i think there is a GPT partition table on the hdd)
- for the installation of openSUSE a new hard disk was bought and plugged into the PC (it is a 2TB hdd)
- the installation went fine, not problems or errors occured, the whole new disk was used for root (2 GB as swap) no addtional partitions

After the installation finished i the pc rebooted, and started windows, so i checked the boot settings in the bios and changed the new HDD to highest priority (Winodws partition was next in line).
After that, windows started again, so i checked the bios again and made the usb installation-stick second in line (the new hdd stayed first and windows became third), this resulted in the usb stick booting.

I have not the slightest clue whats wrong here, i assume it is something about (U)EFI, i do not know, what can i do to investigate further?