If you are looking for the Silent Hunter 4 version 1.5 patch
expansion. In this franchise, the v1.5 "patch" is not a separate free download but is integrated directly into this paid add-on. Official Download Sources Silent Hunter 4 1.5 Patch Download
Workaround: Download the "Starforce Removal Tool" before installing, or simply buy the GOG version of v1.5 (which is DRM-free). Your sanity is worth the $10. If you are looking for the Silent Hunter 4 version 1
American skippers aren't left out. The 1.5 patch introduces the (the ultimate US diesel boat) and properly refines the Balao-class with correct late-war radar and AA suites. Silent Hunter 4 1.5 Patch Download