Finally! It took an update of the BIOS to fix the problem. Win7 boots into UEFI now and is installing as I am writing this.
Many thanks to this great forum Apparently it can be hard to rely on older hardware. Every thing else was done correctly.
Maybe the Tianocore EFI loader helped this, since it was placed on the USB.
Used this version:

Use the readme file to get the basic information and install tianocore on usb.
Then transfer a windows install disk to the usb by following step 8 from Brinks tutorial:
UEFI Bootable USB Flash Drive - Create in Windows

Hope this will help some