My new 100gb Portable HD

I just a bought a segate 100 gb portable external hard drive. It came with a Y type cable. The two ends are USBs to the computer.

The manual says that if the drive doesn't have enough power from one cable, then connect the other cable too. The first USB end (green) is POWER+DATA and the other end (blue) is POWER ONLY. There is no mention of what would indicate less-than-enough power. I connected the green end and the hd started beeping and the light blinking. The computer didn't recognize the hard drive either. Then I connected the othe end and then it was fine.

I will try it with the Work computer tomorrow but is this pretty common to have to use two USB cables for Portable Drives?

its not really that common. Most external/portable hard drives draw power from a power outlet because hard drives usually require more power than usb ports can supply. When I refer to enclosures, I mean 3rd party enclosures which you install the hard drive yourself. I don't know much about brand name enclosures like segate, wd, maxtor.

well this one is supposed to be directly powered off of the USB port without any power supply. that and its size is what makes it very portable