We have produced a small zip archive that contains a test php file. Please download it and follow the instructions below.
When you visit the url you should look for a box with a 'Powered by Zend' logo. Look for the text that we have underlined in red below. This will tell you if Zend Optimizer is installed and if so, which version.
You should now know if your server has Zend Optimizer installed. If it has, make a note of the version number (3.x.x or 2.x.x) and proceed to the download area.
If you do not see any mention of Zend Optimizer then it is likely not installed. You can download zend optimizer for free from zend and install it (if you own your own server that is). If you do not run your own server, you could ask your host to enable it (sometimes you need to ask), or, ask them to install it if they don't have it installed.