usb 2.0 pci card for notebook not working

ok i just reinstalled my OS on my latop. i bought a 2.0 card from best buy not that long ago. i got it for the use of a external hard drive that i have. before i reistalled the OS i installed the usb card fine. it works great with the external hdd. but now since i reinstalled i cant get the card to work with the hdd. iv tried installing multiple times and cant figure it out. iv read on a few things online that it might not be getting enough power to run the hdd. every time i plug in the hdd my computer locks up and i have to pull it out to unlock it. but why would it not work now if it worked before i rebooted. mabe if there is a way to somehow get power to it or something else im not sure. any help with be appreciated.