How can I do a SQL Server 2000 bak?
Here is a process that you need to go through for upgrading from SQL Server 2000 to SQL Server 2014.  

http://sqlmag.com/sql-server-2014/sql-select-steps-migrate-sql-server-2000-sql-server-2014

You will see that you need to 


Restore a SQL Server 2000 backup to SQL Server 2008 as one step, followed by 
Restore of the (now upgraded) 2008 version to SQL Server 2014.


If you only have .mdf files (not a full backup of the database) then you will need to create .ldf (log) files for the instance. This is not a recommended method for restores, but may be what you need.  Perhaps use marc_s script:

CREATE DATABASE Test_Data
ON PRIMARY 
(FILENAME = N'D:\Test_Data\Test_Data.mdf')
FOR ATTACH_REBUILD_LOG
GO 


Or, there are several posts out there about attaching a database without a transaction log file.  One random choice:

http://www.mytechmantra.com/LearnSQLServer/How-to-attach-database-without-a-transaction-log-file-in-SQL-Server.html

If your SQL Server 2000 .mdf was from SQL Server 2000 SP4 then you may be able to attach it to a SQL Server 2008 server.  If the file has been corrupted, of course, then there is little to be done.  

From this location you can apparently download the MSDE engine and SP 4.  The MSDE engine will only handle a 2GB database.

https://msdn.microsoft.com/en-us/sqlserver/bb895925


Microsoft SQL Server 2000 Desktop Engine (MSDE 2000) Release A
Microsoft SQL Server 2000 Service Pack 4


MSDE has many limitations, including only 2GB databases.  (And it has been so long since I used it that I do not remember all the problems and limitations.)  See:

https://technet.microsoft.com/en-us/library/ms165672(v=sql.90).aspx

If you need a full version of SQL Server 2000, then I would suggest that you talk to other SQL Server users in the area and find one who still has retained an original install disk.

There are websites that say they have the media, but I cannot recommend them.