Knowledgebase
How to make sure your Magento sample data shows after installation
In order for the sample data to show up properly after a successful Magento installation with sample data, make sure you do not set a custom prefix during the Magento installation. The sample data contains no database prefixes and if you set one during installation, the sample data will not be displayed.
You will either have to change all tables in the sample data sql or complete the Magento installation without setting a db prefix.