WHAT IS THE INPUT VOLTAGE AND AMPS OF A 500 GB WD EXTERNAL HARD DRIVE. I LOST MY ADAPTER

Jim, take he hard drive with you to a electronics shop and let them match it up to a universal power supply/adapter.
Amazon com 12V Iomega LDHD UP External hard drive replacement power supply...

Iomega Prestige 500 GB USB 2 0 Portable External Hard Drive 34169

http://www.aliexpress.com/price/iomega-power-adapter_price.html

NEW AC Adapter For Iomega LDHD UP2 External Hard Drive Charger Power...

Yes, this model is certainly compatible with Windows 7.
If you've lost the AC adapter and need to replace it, the most important things to look at are:
1) the size of the plug
2) the input voltage of the drive
3) the minimum current in Amperes (A) or milliAmperes (mA) required

For units manufactured after June 1st 2008, these are the requirements:
12 Volts
1.5 Amps
18 Watts

Western Digital recommends only using original WD power adapters.

See here for more information: https://wdc.custhelp.com/app/answers/detail/a_id/1378/related/1/session/L2F2LzEvdGltZS8xMzg3MTQwNTQxL3NpZC9aNG1NbVZIbA%3D%3D

Tip: sometimes you can find a cheap and original power adapter on eBay or Craigslist or Kijiji.

you may have a bad drive,but first dose the drive power up not just light up can you hear the drive.
what you have in the box is just a nornal HD in an external box. you can if "absolutely nessesary " remove the HD and put it into your PC as a second drive.
but first you need to know if it is running and if the WD My Book power supple is working.
Have you tried using a different USB cable? a different power supply of the same Voltage & amps.

An external storage-device has four major components:

* the USB cable

* the power-adapter

* the disk-drive inside the enclosure

* the USB-to-disk-drive adapter inside the enclosure.

One of these components has failed.

Try a different USB cable.

Try connecting to a different USB port on your computer.

Try connecting to a USB port on a different computer.

Take a "multi-meter" and measure both the voltage and amperage output from the AC adapter, and compare with the specifications on the label on the adapter.

Open the enclosure, and remove the disk-drive, and then connect it as a "slave" disk-drive in a desktop computer, to see if it works at all.

Purchase a new, compatible, disk-drive, and install it in the enclosure, to "revive" your external storage device.

Get the part-number and serial-number from the label on your disk-drive, and access the manufacturer's web-site, and use "check warranty status", to see if they will replace the device, at minimal cost to you.

Note that W.D. has a "Customer Loyalty" program -- you can buy a new W.D. device, through the W.D. web-site, at a significant discount.

There exist commercial "data recovery" services that can try to repair your device, just long-enough to rescue and copy your files. For example, see: https://services.seagate.com/index.aspx?lng=en-US for a "no data - no charge" guarantee.

Check the label affixed on the unit. It should indicate the power requirements. If not, go to the Western Digital website and locate the specifications for this particular model.

output is 12v and 2 amps, you can go higher in voltage and amps but i wouldn't go lower, it would cause the little motor inside to heat up

AC INPUT VOLTAGE - 100-240VAC
AC INPUT FREQUENCY - 47-63 Hz

NO, they are not all multivoltage. Especially if you bough *** in the states as a 110v. You will need to have an external voltage adaptor in use.

Output voltage is 12 volts at 2 amps. 24 watts.
See if it looks like this,

http://cgi.ebay.com/12V-AC-Power-Adapter-For-Seagate-FreeAgent-Pro-drives_W0QQitemZ260396021307QQcmdZViewItemQQimsxZ20090419?IMSfp=TL090419153008r30934

they all use 12V , so just get any 12v transformer that fits
the amp is i think 3.1amp or near.