You're right that it could be easily done in any other language on a modern Unix, but µTorrent is written extremely closely for Win32 -- which is exactly why it

You're right that it could be easily done in any other language on a modern Unix, but µTorrent is written extremely closely for Win32 -- which is exactly why it's so terrific on that platform. The thing is brimming with features, insanely fast, and the self-contained executable is only 282kb! My favorite torrent client is rtorrent (written in C), which has a lightweight featureful ncurses interface, and its executable on one of my Linux x86 boxes is 680k + 586k for libtorrent! He's almost certainly right that you could never, ever, make it so fast and small using any other language ON WINDOWS.