You don't delete the "compress old files".
It is asking a question. It is saying "Do you want me to compress those files".
In a normal, properly working system you can safely let the computer compress old files to save disk space.
It will fail if you have bad memory or bad hard drive but in either of those cases you have other problems anyway.
1/3 of highway deaths are caused by drunks. The rest are by people who can't drive any better than a drunk.