PFGW (PrimeForm/GW) is a primality proving program that performs deterministic classical tests wherever possible and allows probable prime tests of arbitrary expressions. It is available for many x86 platforms, including Windows, Linux, and Mac. It uses the George Woltman libraries (gwnum), as developed for the GIMPS project, for high-speed PRP and classical testing of arbitrary forms. There are both 32-bit and 64-bit builds available. A Windows GUI version of PFGW, called WinPFGW, is available that can run on Windows XP, Windows Vista, and Windows 7.
The previous version of the program, "PrimeForm for Windows", is now obsolete. It is a sister program to Yves Gallot's proth.exe and uses the same mathematics libraries with it. It is still available for users who prefer a GUI, but it is several times slower than pfgw.