My USB Drive is no longer recognized

I have a new macbook computer and started to download some data from an external seagate 320GB drive connected through USB. The problem is my battery died before it was finsihed and then I separated the USB line. Now I can not get the drive to be recognized. It is found, but it says that it needs to be formatted. When I plug it in an XP running machine I have the same problem. Does anyone have any suggestions of how I can recover the data?

Try to repair the drive with Disk Utility. On OS X that's in /Applications/Utilities/. Good luck.

There are various places that can recover data off hard drives, as a last resort. See Technical problems with a hard disk.

Also, never unplug a USB hard drive without first ejecting it in the Finder.

The best recovery utility I've found for Macs is Data Rescue. There's a free trial to see if it can fix the disk, useful as the full version is 99USD.

People say that, but I've never shut down any device, and I've used loads, before unplugging it and have never had a problem. Perhaps I've just been lucky.

Fortunately my neighbor is an IT repair person for Siemens and has the software that they first try to rpair the disk. It is recognizing the data, but as the data is 300 GB it will take at least 3 hrs. But it looks hopeful.

Keydeck, if you want performance with any hard drive, you need caching. If you have caching, you need to write asynchronously. If you write asynchronously, you shouldn't unplug the hard disk without notice. If it's not using a log filesystem or the file system doesn't use atomic writes, you may even corrupt the file system just by unplugging the device (that's what probably happened in brokenm's case).

Ext. USB Hard drives are normal Hard drives that at put in an Ext. case with a small cheap
IDE/USB adapter. Try taking the HD out of the case and installing it directly in your
computer. If you only have a laptop then your going to need to borrow a tower/desktop
PC to do this. Then try copying your Info off. HD's are very robust devices and simply
unplugging the thing from the USB port while moving data, won't screw them up.

It' more likly that the USB/IDE adapter in the Ext. case got fried and the HD within is still good.
If the Ext. drive is small (Notebook Hard drive) then you will need a 10 Eur adapter to change
the pin size so you can put it in a desktop PC.

No need for Recovery software just yet, esp. if the drive isn't even recognized by the computer first.

@DK title is slightly misleading to a techie. From post it seems device is found but not a file system, so doesn't sound like a HW issue.

Ah, in that case your going to have to remove the HD from the case and connect it to an IDE connector, as most of the good Recovery programs can't or won't work with USB Devices..