ApiHooks 6 is a set of libraries and tools for advanced
process modification and noninvasive debugging
on Microsoft(R) Windows(R) NT 3.51, 4.0, 2000, XP, 2003, Vista, 2008, 7 x86 and x64.

AH6 is not compatible with AH5.
It can hook even autochk at boot time or
a process before its full initialization (= before DllMains of statically linked modules are first time executed).
Works under any account and doesn't modify files.
There's still no need for services or kernel drivers.

ApiHooks 6 is free.
Current version : 6.8
Previous version : 6.6
Previous version : 6.51
Previous version : 6.5
Previous version : 6.4
Previous version : 6.3