Do you have some files in the folder C:\Users\user\AppData\Roaming\eTeks\Sweet Home 3D where user is your user name?
It's the place where are stored preferences and the models you imported. If it contains only a file named preferences.xml and some sub folders, I fear you lost everything.
But maybe you work under a new account, in which case you would have just to copy the content of the matching folder in the old account.