I first looked through the OpenCart Online Documentation. The most current stable release as of this writing is OpenCart v18.104.22.168. OpenCart requires PHP, and MySQL. I currently have both installed on my Windows Server 2008 platform. It should also work fine running under Windows IIS 7.
As a side note, the OpenCart Tools section outlines some great suggestions for free tools. I use some of them, like Jing, others I’m excited to check out.