From a purely windows perspective, there are a lot of tools that can help as well.

The very excellent Process Explorer from Sysinternals will allow you to see what perl.exe has threaded beneath it - I often find with lots of disk intesive operations that Perl itself takes up very little CPU, but the Kernel itself is running quite high (as it's that that's handling the disk IO).

You may also want to try bumping up the thread priority (vanilla task manager can do that), but I doubt it will make much difference.