my computer only has a 200w power supply and i want to run a hd4850 graphics card in it. now i have a 120w 12v power brick spare now can i use it to power the graphics card? i was going to hook the 120w power supply up to the pci-e power connection on the graphics card. my main worry are that the slight voltage differences between the two power supplies will damage the graphics card internaly. and will the graphics card keep running even after i power the system down because it still has power?