I have a window in the frame wall of the walk out basement that won't stop leaking. I removed the siding from around it, removed the window and discovered there was no caulk any where. I siliconed around the frame and reinstalled the window and siliconed around the lip and screws, replaced siding. It still leaks. As a note there is a window above it on the main floor but it doesn't leak. Any ideas on how to permantly fix this? Thank You.

You found no flashing either? Windows are normally flashed with a rubber membrane rather than caulk. If you have the siding off you should be able to install rubber adhesive flashing, sides overlap bottom and top overlaps sides.