Convert WLMP to MSWMM

Newer versions of Microsoft Movie Maker are no longer capable of exporting to the previously used .mswmm format; only to the new .wlmp format. That means that it's most likely impossible to directly convert .wlmp to .mswmm (Windows Live Movie Maker Project to Windows Movie Maker Project).

You might need to recreate the project from the original source data (images or video) in Windows Movie Maker for Vista.

Simply put, it is impossible to convert WLMP to MSWMM directly.
Thus, there is no so-called wlmp to mswmm converter or a free online .wlmp to .mswmm converter to be found.