Yea what xeromist said, its probably a problem with the client folder you have, Im running my OS on a SSD and steam on HDD, and its working fine, just uninstall and reinstall steam after making a copy of the folders. If i were you though, i would go ahead and do a fresh install of everything, you never know if the client could have gunked up the game files too.
Good luck man, hope it all works out!
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