When I click on "Check for Zenphoto updates", I get:
"Fatal error: Call to undefined function sprinf() in C:\Program Files\wamp\www\zenphoto\zp-core\admin.php on line 980"
What do I do?

That is a typographical error that we will correct. However, what it is telling you is that you are not on the latest version, so download version 1.2.2. (That will still have the error, but since it will be the latest version until 1.2.3, you won't get the failure until it is time to upgrade again.)