Open outlook 2007, Go to menu and chose…
Tools > account settings > data files
You will find the screen like shown below:
Now select the 1from the listing which shows default (your active email account data file). As I have marked as round in above screen.
After selecting the file from list, now click on the “Open folder” as shown in above screen.
Clicking on Open folder will take you to the folder where your outlook data file is located,
And you will find that file selected in the folder,
Now all you have to do is just Copy the data file from this folder and save wherever you want to keep as backup.