To restart the SQL server, please follow these steps:
1) Log into your server through Remote Desktop Connection (instructions for connecting to your server through RDC can be found here).
2) Click Start, Programs, Administrative Tools and select Services.
3) Scroll through the list and select SQL Server (SQLExpress) or SQL Server (MSSQLServer), depending on your version.
4) Click the Restart Service button.
5) You should see the service stop and then start.