Unfortunately, this software is discontinued for a long time. This means that the developer isn't going to release any updates or offer support for it anymore. There is no way you can install the software on Windows 7.
In the case of alternatives, you will need to download and use an application that is compatible with Windows 7. Also, depending on the format in which you currently have your data, visit the Software Informer's website. By doing this, you are able to find and download an application that can open or convert your data from DrafixCAD.