External Drive No Longer Recognized

I've got a Western Digital external HDD 1021. I used it on an XP computer for a year or two before I purchased my current Dell Inspiron M5110 laptop with Windows 7 installed. I've had the laptop about two years now and I've been using the external drive as needed, plugging and unplugging on a regular basis.

Last week, I plugged in the drive and my computer did not recognize it. The HD hums and the light is on (not blinking), but I can only see it in Disk Management. I've tried it on other computers (an XP and a Windows 8) and with another USB cord. Neither attempt makes a difference. Disk Management will not recognize it as a volume to let me assign a letter. It only lists it below as "Disk 1: Basic: 1863.01 GB: Online; Unallocated." I could format the drive to get my space back, but I've got about 1 TB of data on the drive and would prefer not to lose it all.

When the drive first started giving me problems, three or four days before it quit, a run through cmd: chkdsk /f would solve my problem. Now cmd doesn't recognize the drive. I uninstalled and reinstalled the driver, but that didn't help either. I've exhausted my knowledge on the troubleshooting front. Any help or suggestions y'all have would be greatly appreciated.

Thanks!