Im looking for a western digital 640 gb hardrive manual

Try to plug the hard disk usb cable to backpanel of the CPU.

These kind of "docks" can be found on ebay for drive diagnostics or file transfers without opening your computer.

Does it show up as a drive in the Device Manager?

You might look in Control Panel > Administrative Tools > Computer Management

Go in Disk Management along the left side...

You might have to make it into a Basic Disk ... before it gets a drive letter. Trying to remember what I just did in Vista when I got a Seagate FreeAgent external USB drive. Mine was already NTFS formatted, I would imagine yours would be too.

download the manual from here
http://support.wdc.com/product/download.asp?level1=1&lang=en
choose the correct model and download the manual

On anothre computer, go to Western Digital's web-site, and download their "Drive Fitness" software. Burn to CD, or write to 3.5" diskette.

Boot your computer from the diskette/CD, and run the test, to see if the hard-drive is "failing".

Note that Western Digital has a "Customer Loyalty" program.
If you have the serial-number from your current hard-drive,
you can buy a new hard-drive, online, at a discount.

warrenty will be void if you open the casing
but warrenty for hdd will remain .. so if under warrenty get it replaced, as it is, if data required the warrenty should not be concidered and data recovered, probably the hard drive may not have got damaged , so dont get fooled if some one says data recovery . if you cannot do it hire an expert guru for data recovery.

check warranty on the Western Digital Website and send back if still under the one year. Thats what I have to do...

http://smallbusiness.chron.com/repair-corrupted-hard-disk-drive-data-66855.html

try using the dynamic drive overlay supplied with the drive? Your MB may not be able to handle it.

That's normal. Storage manufacturers consider 1 GB at 1 billion bytes (1,000,000,000 bytes).

Computers, however, use base-2 arithmetic, and one kilobyte is 1024 bytes, one megabyte is 1024 kilobytes, and one gigabyte is 1024 megabytes. This all multiples to 1 gigabyte according to the computer is 1024^3 or 1,073,741,824 bytes.

Take 320,000,000,000 and divide it by 1,073,741,824 and you get 298.023223876953125, so your computer says your "320GB" drive is 298GB.

There's a standard for base-2 (binary) measurement terminology (gibibytes, mebibytes, kibibytes, etc), but few people seem to use it.
http://en.wikipedia.org/wiki/Orders_of_magnitude_(data)