I have wampserver 2.5 installed on my machine which has PHP 5.5.12
But I need to setup and application which is built in PHP 5.2. So how do I use this 5.2 version of PHP?
To get that far back in history, you may find it easier to install one of the old WampServer 2.2 releases.
You can find the old releases here
There is a special extension to WampServer 2, which will let you install PHP 5.2.11 in your WampServer.
Here's the download link: WampServer Extension for PHP 5.2.11
WampServer Extension for PHP 5.2.11 - is not the best solution, as you could get compatibility error error image. Better to use RiggsFolly solution and install older wamp version.