After upgrading to Windows 8 from Windows 7 or Windows 8.1 from Windows 8 some games downloaded from Steam may no longer launch. This issue can be resolved by using the steam client to verify game cache. Instructions can be found on Steam's webpage.
https://support.steampowered.com/kb_article.php?ref=2037-QEUH-3335
https://support.steampowered.com/kb_article.php?ref=2037-QEUH-3335