I cant connect to my cable modem using ethernet...

I have a dell 2350, and ive been using a usb connection these past few years, and now i want to change to ethernet so i can install my wireless router for my laptop...

but there seems to be a problem... It wont connect to the internet, so i try to pop in the cable internet cd

and this is what i get everytime when i try to install "DOMAIN NAME SERVER (DNS) FAILURE". i have a motorola surfboard sb5100 modem...

i tried searching, and i found this link http://support.dell.com/support/downloads/download.aspx?c=us&cs=19&l=en&s=dhs&releaseid=R64645&SystemID=DIM_PNT_CEL_2350&servicetag=&os=WW1&osl=en&deviceid=3597&devlib=0&typecnt=0&vercnt=3&catid=-1&impid=-1&formatcnt=1&libid=5&fileid=84196

but... it still doesnt help...

i really wanna get this wireless modem to work! help