First off download metal slug 4 from http://www.fc5.net/HG0103/downloads/mslug4.zip. Next download the kawaks hack from http://www.geocities.com/yansbusi/Kawaks1.44aHack.zip (Note: Copy this the url in to the address bar)
That is all you need to do!
Coming soon is: Secret of King of Fighters 2001 revealed! How to make it work on WinKawaks!