How can I do a CPU cache flush in x86 Windows?

I am interested in forcing a CPU cache flush in Windows (for benchmarking reasons, I want to emulate starting with no data in CPU cache), preferably a basic C implementation or Win32 call.

Is there a known way to do this with a system call or even something as sneaky as doing say a large memcpy?

Intel i686 platform (P4 and up is okay as well).