APISpy32  Version 2.0    No Registration Required  
27-Jul-99 280K Win 95/98/NT  Freeware  Never Expires  No Install  
2 min at 28.8K  1 min at 56K  <1 min at ISDN 128K  
A system-wide API spying utility capable of intercepting API calls made by all active Windows processes and their attached DLLs. It gathers information about each API call including input parameters, return value and origin address. Complete source code is included.  
Published by Yariv Kaplan  APISpy32 Home Page