If you open the Skyrim launcher and the "DATA FILES" is greyed out then you need to do this:
"If you are having trouble enabling some mods and the 'DATA' option is grayed out on the launcher, go to 'Users/*yourname*/My Documents/MyGames/Skyrim' and look for the file SkyrimPrefs.ini.
Open it and find the [Launcher] section. Under that section, put the line bEnableFileSelection=1 and save the file. Next time you pull up the launcher, it should be there."
"I downloaded, played, and beat the dragon born DLC the day it was released on steam. Still, even after playing the DLC for several hours, there somehow is no Dragonborn.esm listed in the data files on the launcher or in the plugins.txt file." - SKUMMY2014 on the Skyrimnexus forums.
You didn't say whether or not you tried to go to Solstheim, which you may be able to do even without the Dragonborn.esm listed.
well I downloaded hearthfire to see if that will show up. But it had no add-on menu. but I bought a ne windows 8 computer and I was thinking maybe they didn't support windows 8 yet. but I'll play for a few hours to see. But I recently saw that this ting has happened beore and no issues were soved for the same problem I had.