I'm assuming you saved it to the right location. If you never changed the User Data Folder location it's
My Documents\Sports Interactive\Football Manager 2008\db
on XP (off the top of my head can't remember what the Vista equivalent is).
Make sure the name of the xml inside the folder containing your database has the same name as said folder. For example if you created a database and saved it to the user directory it should appear as a folder, let's say 'My Database'. When you open that folder there should be an xml file called 'My Database'.
If the xml file name does not match the folder name exactly, then the game will not pick it up as an option. Once those two match the database will appear and it's name in the drop down menu will be the same as the string in the xml:-
<pre class="ip-ubbcode-code-pre"> <string id="name" value="empty database folder"/> </pre>
Off topic but you might want to install the patch as it makes for a better gaming experience. Just my opinion though

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