I have recently purchased a ati radeon hd 4870 ddr5 graphic card. It says i need 2 six pin power cords. But my 450 watts psu doesnt have even one. So can i use a molex adapter to power up it? Can i pin just one six pin power cord (i.e, the one which i converted using the adapter) to the graphic card which needs 2?
No you will need both the 6 Pin connectors to be plugged in. One is not enough.
Yes you can use the Molex to Six pin converter but, if you have a little extra money, you ought to get yourself a better PSU, which will help you out in the future too.
And actually 450W is cutting it too close to the minimum requirement of 500W...
You could end up experiencing random restarts and xyz problems and even damage the other hardware....
IMO: get a PSU. 550 to 650 W should be good enough.