Yeah, but the thing is... that wasn't my point. It is already done in ASM. Just go grab Info-ZIP source code and you can use it inline in any compiler that supports inline ASM (afaik). VB6 is of course out of the list, though you can still use the ASM optimized DLL. That is if you want ASM optimized. VB6 optimized would be good enough for many cases, the only time one has a special need for the most extreme speed is when you compress a lot of files (thousands) or if you compress very big files. And even then it might be the computer harddisk which cause the most slowdown, knowing the processing power of a modern computer.