2 WD drives, one works, one doesnt

Are both of these drives the same size and model?  Sometimes Windows has problems with that. If that is the problem this  http://community.wdc.com/t5/My-Passport-for-PC/Copy-files-from-one-drive-to-another/m-p/277504/highlight/false#M7587 should fix it see post 11.

Joe