If you rename or move the folder containing your magento installation or want to change the domain you won’t reach it anymore because the base_url is saved in the database and used for redirects. So connect to your database and change the URLs saved there:
The URLs are saved under core_config_data and can be retrieved by:
SELECT * FROM core_config_data WHERE path LIKE '%base_url';
Then just adapt the result and don’t forget to clean the cache.