python os.listdir() muestra archivos protegidos

So, I'm trying to make myself a Python script which goes through the selected Music folder and tells the user if specific album doesn't have an album cover. It basically goes through all the files and checks if file[-4:] in (".jpg",".bmp",".png"), if true, it found a picture file. Just to make it clear, the structure of my folders is:

• Carpeta de música
  • Arctic Monkeys
    • Humbug (2009)
    • Suck it and see (2011)
  • Morfina
    • Cure For Pain (1993)

.. and so on. I'm testing the script to find if there's a missing cover in my Arctic Monkeys directory, and my script goes through the "Humbug (2009)" folder and finds AlbumArtSmall.jpg which doesn't show up in the command prompt so I tried "Show hidden files/folders" and still nothing. However, the files show up once I uncheck "Hide protected operating system files", so that's kinda weird.

Mi pregunta es - how do I tell Python to skip searching the hidden/protected files? Revisé el ¿Cómo ignorar los archivos ocultos usando os.listdir ()? but the solution I found there only works for files starting with ".", and that's not what I need.

¡Aclamaciones!

Edit - so here's the code:

import os

def findCover(path, band, album):
    print os.path.join(path, band, album)
    coverFound = False

    for mFile in os.listdir(os.path.join(path, band, album)):
        if mFile[-4:] in (".jpg",".bmp",".png"):
            print "Cover file found - %s." % mFile
            coverFound = True
            return coverFound

musicFolder = "E:\Music"   #for example
noCovers = []

for band in os.listdir(musicFolder):    #iterate over bands inside the music folder
    if band[0:] == "Arctic Monkeys":    #only Arctic Monkeys
        print band
        bandFolder = os.path.join(musicFolder, band)
        for album in os.listdir(bandFolder):
            if os.path.isdir(os.path.join(bandFolder,album)):
                if findCover(musicFolder, band, album): #if cover found
                    pass                                #do nothing
                else:
                    print "Cover not found"
                    noCovers.append(band+" - "+album)   #append to list
            else:                       #if bandFolder is not actually a folder
                pass
        print ""