Home setup wife breaking balls

Hi there ,

My location is Seoul South Korea and we get a 100mps line here in our apartment.
I was using the line for a single computer for a while which was great and now we got a notebook, and so I bought a
Gateway gw450A (not sure what to call it) it devides the WAN into several outputs so more computers can use it.

Now the problem , major bottleneck jam-ups. When using the 100mps line on both computers one of the two has problems even surfing the web. I do have some downloads going on most of the time in the background on my desktop (Computer1) utorrent.
Which of course could be the cause , but even without downloading bandwidth being used jam-ups occur ever too often.
I do realize that this question/problem is not new , but this field is just to unfamiliar to me to , and have to ask this way.

I thought about maybe ditching the cheap gateway and getting a wireless transmitter for my desktop and just let the notebook pick up the wireless bandwidth that way ( Notebook has wireless LAN) Lenovo N100 3000 0768 ...

I need a solution where jam-ups are a thing of the past ... ^^

Thanks for now ,

Ralph