Step 1 : Download New version of the Sample Data zip file from Magento Website or Click here for download
Step 2 : Extract the zip file, It will contains a mysql file and a folder with the products images named as media.
Step 3 : Import sample data sql file into your magento database.
Step 4 : Replace the old media folder with the new media folder downloaded with the Sample data and change the folder permission 755 or 777,In the root of your Magento installation.
Step 5 : Now go to your admin panel and Refresh the Cache and Reindexed the Data, Remember that app/etc, var, and media folders are writable. They should be writable. Change their CHMOD to 777.
Step 6 : Now Go to the front end here you will see all the data as well as the categories also.