actually this happens bcoz
when you watch a video or play a game
it get saved in ur temp folder
than when u try to download it, it just get copied from temp folder to the download location u specify thats it
so it just take 1 sec
nope thats not the thing. it happened to me once. i got a speed of 2mbps. it increased slowly from 256kbps to 2mbps. it only happened once at night. i was gettin that speed for watever i was downloading that time.