I have a hard drive that has an enclosure is there any way to take an internal 3.5hard drive and convert it to an only usb cable portable hard drive with no power cord?
No. Not a 3.5 hard drive. You can do it with a 2.5 laptop drive because the drive mechanics and electronics require less power. A 3.5 drive requires too much power for USB to provide. Though... In the near future, you will see USB ports that are capable of supplying more power than the standard .5 amps that USB currently provides. So after they come out, you might see it being a possibility then.
