Thx for your replies!

Unfortunately, I cannot post photos at the moment., because I am at work atm. But I will as soon as I am back at home.

...and yes, the both molex were powered when the graphic card (gc) was plugged into the pci-e slot. I tried a lot of different installations.
A friend of mine is guessing that it must be an option within the bios. everything else should be correct.

Sometimes it seems that the gc hasn't enough power... it is just a feeling... I will also try another power supply today evening just to be sure that the ps isn't faulty.
the ps is brand new... but who knows... the first mainboard I have ordered was also broken.

or... could it be that something else is blocking the correct startup of the gc?
is there any step by step tut to follow or should I continue with try and error?