Toshiba and WD external HD not showing up in my computer

Hello,
I have a few different external hard drives that wont show up in the 'my computer' panel on my windows 7 computer.
one of them is brand new and i also have 2 more that are a little older but they are all doing the same thing.
I have tried every USB port and other things work when i plug them into those ports, but pretty much all my external hard drives aren't showing up at all. My pc makes the sound to say it recognises that there is something plugged in and they show up in control panel>devices but not in the side panel under my computer. please help, i have tried a few things on this forum that dont seem to be working and am completely stuck.

Thank you :D