The first thing to do is to verify that you can write to the folder that is presenting the "Access Denied" message in the installer.
So, close out of the BigOven installer, and open Windows Explorer.
Navigate to the folder as named in the message, and try to create a folder called "My BigOven Recipes" in your "Shared Documents" folder, and then, try to save, say, a TXT (Notepad) or Word document into that folder. If you cannot, then please see Windows Help to make sure you have full read/write permissions on that folder.
If you can save to that folder, then perhaps the Access Denied message is coming from the source location, not the destination, though the Installshield error message does suggest that it is the destination that is denying you write-access.