@Steveorevo beat me to the reply, but i typed so much and dont want to waste it, lol but basically what Steveorevo said.. or..
what i do is,
1. create a new database in phpmyadmin, create a new clients folder in your www folder,
2. make a copy of your current wordpress files in the www folder and copy them to the new clients folder.
3. edit the wpconfig file in your new clients folder to reflect the new database (credentials) you created.
4. open my phpmyadmin and find in the wp_options table, the siteurl and home values and change them to reflect your clients url e.g (localhost/client)
5. Navigate to localhost/client in your browser
Basically you have made a copy of your site but this way all your plugins etc will be preserved and you wont have to install them all over again, you might get some broken image references but you can fix those with a plugin
hope it helps