search a file in a local system (windows-D drive)

hi guys,

i am new to java, i am facing some problem when searching a file in local system, my code is

Java Code:

import java.io.*;
import javax.swing.*;
import java.applet.*;
import java.net.*;

public class SignedApplets extends Applet{
/**
*
*/
private static final long serialVersionUID = 1L;

public void init(){
new WriteText();
}

public class WriteText {
WriteText(){
try {
String str = "D:\\Projects\\Java\\Applets\\Experiment\\WriteToAFile\\aff-masters.zip";
File f = new File(str);
if(f.exists()){
JOptionPane.showMessageDialog(null,"File Exists!");
}
else{
JOptionPane.showMessageDialog(null,"File not there!");
String link = "http://www.goldcoastwebdesigns.com/dl/aff-masters.zip";
try
{
AppletContext a = getAppletContext();
URL url = new URL(link);
a.showDocument(url,"_blank");
}
catch (MalformedURLException e){
System.out.println(e.getMessage());
}
}
}
catch(Exception x){
x.printStackTrace();
}
}
}
}
html
Java Code:

7

and policy
Java Code:

grant{
permission java.security.AllPermission;
};
it is working fine when searchable file and applet(related things) are in same directory.

suppose i wanted to search entire local drive(D) for a file. what i have to do... please help me in this scenario.

-------
Thanks and Regards,
Srihari(:~