It was suggested i make an FAQ for this so here ya go.
Just for anyone new to SQL Server (As I just assisted another with this problem) Do not put data you want to keep into the TEMPDB created automatically by SQL Server.
I had a client who wanted to re-create his DB, he moved all the data into TEMPDB, droped the old database, but then just as he was creating the new DB, the Server PC locked up and crashed.
When he rebooted all of his data was gone. This is quite normal apparently with SQL Server, If you read the docs you'll see that SQL Server will drop and recreate the entire TEMPDB database everytime the server is started.