import os

def rename_files(directory):
    for filename in os.listdir(directory):
        if "_" in filename and filename.endswith(".mkv"):
            new_filename = filename.replace("_", " ")
            src = os.path.join(directory, filename)
            dst = os.path.join(directory, new_filename)
            os.rename(src, dst)

# Example usage:
rename_files("D:\Series\Stargate\SG-1\Season 1")