Well you can sort them anyway you like in the file system and if you want random sort, sort by file size, heh.
Now, trying to create a random method of playback is trickier and depends on your media player. Some players allow you to create playlists and might even have a"randomizer" if you drop all mp3s into the same folder. There might be some new apps out there since I've looked around that can crawl across directories and I don't know what limitation Windows Media Player has because I don't use it.