I downloaded Red Hat's Open Source POSIX Threads for Win32and built the DLL on my system. I linked it to a Pthreads program on Windows and it ran correctly. It's a pretty easy way to get Pthreads programs working on Windows. I didn't do any performance experiments but I don't expect a significant performance loss. The Red Hat Pthreads implementation just wraps equivalent Windows threading functions.
I did an experiment to test whether the Intel Thread Checker could analyze a Pthreads program on Windows. The Pthreads DLL was built with the /Qtcheck option in the Intel compiler. My test program was also built with the /Qtcheck option. Data races were deliberately introduced into the program. Thread Checker correctly identified the data races, their locations in the code, and the variables involved.
Using Pthreads on Windows