How can I mount or extract TWRP Nandroid backups in Windows?

Every so often, I need to extract files from a backup. I'm aware Titanium Backup can do this, and there are no doubt other apps capable of the same, but I want to do it on my PC where the backups actually reside. Files with the .ext4.win extension are simple enough -- just open in WinRAR or similar -- but .emmc.win files are another story. Are there any tools to extract, or, ideally, mount .emmc.win files in Windows?