My housemate keep on downloading from bitcomet, making me and another housemate very hard to surf the net 

I am using Aztech ADSL 2/2+ Ethernet Bridge/Router (DSL 600E) (given by telekom, have set into router)
http://www.aztech.com/DSL-600E.htm

I have tried using bandwidth controller but I do not really know how to use. I do not know how to use the Qos setting also. Can any1 teach? Or teach me to divide the bandwidth or set the idiot fella to lower his rate. 

Your modem support QoS or not? Check the manual for more detail. Dead link BTW.

Yep , does it support QoS or not. IF it does not , there is no way (well there is , unless you wish to convert your PC into a server for this)

Block his bittorrent port lar, settle

Block BT port just make it slower not blocking the whole thing

put 0.0.0.0 netmask 0.0.0.0 for both source and destination ip and netmask
not 0.0.0.0/255.255.255.255...
for the port check ur bitcomet listen port...
set it to low priority..
then done

What is with the big fuss about not allowing him access to the internet 24 hours a day? Just leave the modem switched "ON" on 24 hours basis. There's really no harm to it.