Hi! I have my internet service provider having a maximum speed of 80kb/s when downloading.  Each time I download a file while I'm playing online games, I am always having lags on my game, so I always close my downloading process. Problem is, the download speed ONLY COMSUMES ABOUT 40kb/s which is only half of the maximum that's why I always consider downloading while playing. Upon observing the bandwidth consumed by the online game, it only consumes about 10-20kb/s.  Why is this so? I want to consume the entire speed without having lags on my games.  How can I able to do this? Softwares? Please help...

Contact your ISP.

If your download is 80 then your upload must really suck. When your pipe is full from dling it will limit your upload even more.
 
Dont DL when playing games, or get a better connection.
 
Generally you never get maximum advertised speeds either, you might actually be getting 60 average.

Lets start the diagnose then.  
 
Whats you bandwitdh ? (Up/Down)
 
What game are you playing ?
 
Have you checked for viruses/bots ?
 
Do you have any background downloader/services ?
 
What is your usual latency, and whats you latency when downlding ?
 
Do you download like, a normal download or its Emule or Torrents download ?
 
 
It been a slow day here at work, so if you reply to those i think i can aid ya/give ya some advice to troubleshoot.