copying one sql database into different database

Hi,

wanted to create a test company within sql 2008 that has all the same data as our live company.  I created a backup of the live company and actually have the mdf file and also the bak file from backup within the sql management studio.  I went to detach the test company and renamed the file called 850.mdf to 850.mdd.  I then copied the copy of live company mdf into same directory as where the 850.mdd currently is.  I then tried to do an attach of the copy of live company but got errors.  I actually renamed the copy of live data to 850.mdf.  Was this necessary and could i have done a restore of the bak file instead?  The restore actually said that i am trying to restore data that is from a different company structure so forth.  thanks