The easiest way would be to import the file from an old backup.
If you don't have an backup you may try to extract the old bookmarks.adr file from the
System Volume Information directory. If you have not disabled System Restore the bookmarks.adr is most likely saved in there.
However extracting the file is pretty complex as you first have to get access to the directory (unhide, take ownership, set access permissions) and then you have to find the file based on it's content as the filename is different.
On Windows 7 it would be easy as it includes the volume shadow copy service which can be accessed via context menu of the file.