Complex sentence: An initial project called WinPY attempted to make a replacement open source winmx client, this was the most successful project as a preview alpha version with limited basic functionality was released, however it quickly stalled due to lack of interest.
Split into simpler sentences: An initial project called WinPY attempted to make a replacement open source WinMX client. The WinPY project was the most successful replacement client project as a preview alpha version with limited basic functionality was released; however, it quickly stalled due to lack of interest.