SR-71 Blackbird said:
It will probably run it , but you should upgrade when you can , adapters aren't a great idea for cards.
+1 this. The fact that your power supply isn't equipped with the 8 pin PCI-E power already means it's an older design not really intended to support newer cards. Try to upgrade sooner than later if you can; going to a current power supply, like a 600w Corsair or EVGA bronze unit should be a fairly inexpensive upgrade, about $60.