First of all, I will start by saying that this forum is for the support of Intel's Desktop Board products; it is not for boards manufactured by other vendors. You should be asking this question of (or at the web site for) Fujitsu-Siemens.
That said, I can speculate. There are three primary possibilities for why this is happening:
- The power supply does not provide enough power on the PCIe cable to power this graphics card.
- The graphics card does not provide the support required by the BIOS to initialize it.
- The graphics card has expectation of the board that cannot be met (for example, PCIe support level).
Items 2 and 3 are happening more and more often these days. Motherboards this old (5 Series chipset and 1st generation Core processor are both five generations - and almost six years - out of date) supported only PCIe 2.0 and many of today's graphics cards require PCIe 3.0. As well, many of the BIOS for motherboards this old typically expected a legacy Video Op-ROM to operate properly and many new graphics boards provide only a UEFI Video Op-ROM [Hint: if your BIOS supports UEFI, you might try enabling it. I have seen this work a time or two - but understand that you will probably need to reformat your HDD and reinstall Windows in this case - and you will temporarily have to either reinstall the old graphics card or use the on-board graphics in order to enable UEFI].
Hope this helps. Again, you should (also) be asking Fujitsu-Siemens for help...