there not the full version of the song mate. it only sounds like its full...
this is how it works:
u find a very new track thats only in a set and u here that the main tune and halfway drop is in the set before another tune is mixed in. u go on windows movie maker, chop that bit from the mix and delete the rest. u get the halfway drop, and use that as the intro as well. then, u get the first drop and use it as the 2nd drop as well. then u get the halfway drop again, and use it for the outro.. thats why the outro is usually a fade out in sound... hey presto! a full sounding tune of something thats not out.