My computer cant see my usb hard drive

i just got the 1.5 wd 15 ears and my computer cant see my hard drive when i connect it to a usb docking station. i know the docking station works because i connected my other 250 gig hard drive to it. my computer CAN see the hard drive when i connect it inside to an ESATA cable. the drive worked right when i got it. i plugged it into my mac and formatted to ntfs but when i plugged it into the pc it just disappeared. so now the only way i can see it is if i use the ESATA cable. please help!

Try connecting with USB directly to the computer.  If it shows up, then you know that the signal isn’t getting from the docking station to the mac.  If it still doesn’t show up, try it on another computer to see if it shows up there through usb.  If it does then you know something’s up with our computer.  if it doesn’t show on the other computer, then you something is wrong with the port or the cable.