HI,
As I understand you downloaded a site from another server (possibly online) to a local WAMP server. You’ll need to follow this guide: http://codex.wordpress.org/Moving_WordPress
Also, there are a couple of quick things you will want to check before getting too deep into diagnosis..
A) in order for pretty permalinks to work in Wampserver, you need to enable mod_rewrite. You can make sure permalinks are supported on your Wampserver installation by going to the WampServer icon in the system tray or task bar, select Apache > Apache modules > then scroll down the module list until you come to “rewrite_module”, and place a check mark next to it. Wampserver should do a graceful restart for you, or if not, you may need to restart apache for the changes to take effect.
B) if you downloaded your .htaccess file from your live site, and then transferred that file to your local Wampserver site, you may need to go to the permalinks settings in your dashboard and “refresh” or just re-save your permalinks settings before they will work locally.
configure permalinks for loclhost