Berlkin g usb adapter = slow?

Hello,
here is the basic background of what i have and compared too

Desktop(window xp) + berklin g usb adapter = got 11mb/s (www.speedtest.net)
Macbook(window 7) = got 11mb/s (www.speedtest.net)

So i tested both of my computers and internet speed looked fine, i believe that is the normal speed for linksys wireless router.

here is the problem
i used both computers to download something from a korean server. i understand it gets slow bcause of the distance, but the difference in speed of both computer is totally different although tested equal speed.
macbook gets 200kb/s and my pc with berklin g usb adapter gets barely 60kb/s
i downloaded from same place as well. no difference.
i read some posts about changing channel and changing from wep to wpa. no change at all.

im starting to blame on berklin usb adapter.

so my question is: is it the usb's fault that internet is slow or my pc?

p/s: i only use this pc as a tv kind of. i have connected the pc to tv so i can just watch recorded drama as regular tv.