The recipes wouldn't have been deleted unless you explicitly deleted the "My BigOven Recipes" folder, which is not in the step-by-step list provided.
Much more likely, your recipes are there, but they are in another folder on your PC. See this thread for more information:
http://www.bigoven.com/cs/forums/p/3947/4038.aspx#4038
To bring the old recipe boxes into your new location,
1) Close out of BigOven
2) Look in your "My Documents" folder for a folder called "My BigOven Recipes". This should have your old recipe boxes in it, but BigOven is no longer looking in this folder. It's looking in your Shared Documents folder for this data.
Also look in your folder called "Shared Documents" for "My BigOven Recipes". (On Vista, it's called "Public Folders").
These two filepaths are C:\Documents and Settings\<yourusername>\Documents and C:\Documents and Settings\All Users\Documents if you are using XP. If you are using Vista, the filepaths are described in the link above. Most likely, you have BigOven data in both those locations, with the "My Documents" location being the old one. BigOven only looks in one file location, for performance reasons. Copy all of the folders within your old "My BigOven Recipes" folder to the new location. Be sure to match the file structure, as described in the link above.