Most probably, the partition table's gone corrupt. Don't try to copy/format the drive. Just boot into recovery console using the Windows CD (or use command prompt. I prefer recovery console as I feel it gives you access to powerful diagnostic tools) and run 'chkdsk /r E:' (or whatever is the external disk's drive letter). This should solve your problems. Be advised that this will take quite a lot of time for your 250 Gig drive. I suggest you leave it on over night.
goldeagle2005
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