OS X not recognizing external hard drive

I am helping a friend with a hardware problem on her Mac. It is not recognizing her external hard drive. She tells me it is linked to a program called Time Machine. My experience with computers is limited to PCs using Linux so it took me awhile to figure out how to find the information I needed. In the file manager Time Machine does not sound up. In System Devices it showed the Freeagent (Time Machine) but no matter how many times I unplugged it or changed USB ports the device never showed up in the file manager. At that point I figured it was a problem with the FreeAgent hard drive so I brought it home. When I plugged it into my Linux Netbook the file manager came up and all her files were there. Could someone tell me how to get OS X to recognize this drive?
We tried:
Changing USB ports.
Rebooting the OS.
Tried plugging another thumb drive into a USB port and it was recognized.

Is the drive powered?

Sometimes the USB port does not give out enough power to mount the drive unless it has its own power, or if the port has a few devices, cannot give enough power to that one device

louishen said:

Is the drive powered?

Sometimes the USB port does not give out enough power to mount the drive unless it has its own power, or if the port has a few devices, cannot give enough power to that one device

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That makes sense. I will check that first thing tomorrow. If I remember correctly there is the keyboard, mouse, printer, a camera and at least another couple of devices connected to that computer. Thanks!

SVWanderer said:

That makes sense. I will check that first thing tomorrow. If I remember correctly there is the keyboard, mouse, printer, a camera and at least another couple of devices connected to that computer. Thanks!

Click to expand...

Well I unplugged all the other USB devices and plugged the hard drive into one of the ports on the back of the monitor. Now the light now the Seagate FreeAgent drive only comes on for a few minutes and then goes off. When connected to the Netbook it comes on and stays on and I can access the files system on FreeAgent. Any ideas how to get it to connect on the Mac?