-- Get Current DatabaseID
SELECT DB_ID() DatabaseID;

-- Get Current DatabaseName
SELECT DB_NAME() DatabaseName;

-- Get DatabaseName from DatabaseID
SELECT DB_NAME(4) DatabaseID;

-- Get DatabaseID from DatabaseName
SELECT DB_ID('tempdb') DatabaseName;

-- Get all DatabaseName and DBID
SELECT name,database_id
FROM sys.databases;

Source: http://blog.sqlauthority.com/2011/01/13/sql-server-a-quick-note-on-db_id-and-db_name-get-current-database-id-get-current-database-name/

Problem

You’ve ran out of disk space on the drive where the tempdb files are located.

Solution

You need to move the tempdb files to a new location with sufficient disk space.

1. Execute the following query:

   USE master; GO
   ALTER DATABASE tempdb
   MODIFY FILE (NAME = tempdev, FILENAME = '[new_path]\tempdb.mdf');
   GO
   ALTER DATABASE tempdb
   MODIFY FILE (NAME = templog, FILENAME = '[new_path]\templog.ldf');
   GO

2. Stop and restart the instance of SQL Server.
3. Once the service has been restarted, verify the changes using this query:

   sp_helpdb tempdb

Reference

• http://msdn.microsoft.com/en-us/library/ms345408.aspx
  

A useful link explaining the permissions for built-in system accounts and recommended usage for SQL Server 2008: http://technet.microsoft.com/en-us/library/ms143504(v=sql.100).aspx

More recent information on Windows Service Account and Permissions for SQL Server 2012 can be found here: http://msdn.microsoft.com/en-us/library/ms143504.aspx