It's possible, but very dangerous unless you know exactly what you're doing!
Take a look at this: file system browser class
It would be possible for me, or many other PHP coders from the intermediate level on up, to write you some quick code to do what you are asking, but without more knowledge of your server and which files are OK for users to download and which files should be protected, the code would be a huge security risk.
Also, you should not post enough information about your server for us to write that code, because publishing details about your server on a public site is also a security risk.
