Since the original domain (halftoner.com) is defunct, you cannot download from the official source. However, the software is preserved by several abandonware archives. Caution: Many generic “download sites” bundle toolbars, adware, or malware. Stick to trusted repositories.
Once you have Halftoner 1.7 running:
After installation, locate the Halftoner.exe file in the install folder. Right-click → Properties → Compatibility: halftoner 1.7 download