Deleting older definition files

Hi!

I have an external hard drive and when using Easy Duplication File Finder, I have noticed that there are older virus definitions that have been duplicated because of the backup program I am using (Maxtor). Are the newer deinitions contigent on the older files or can I delete those that are several months old and keep the newer versions (based upon the time stamp?). Some of the file extensions are listed as "xxx.@DB" or "N360_21.1.0.18" for example.

 

Thank you