aspire one wifi problems

[darkfena313]

i'm trying to get wifi to work on my aspire one. i followed the 
instructions from https://help.ubuntu.com/community/AspireOne. when i 
get to this command;

sudo apt-get install build-essential linux-headers-$(uname -r) 

 this comes up afterwards; Ubuntu 8.04.1 _Hardy Heron_ - Release i386 
(20080702.1)' in the drive '/cdrom/' and press enter. the problem is 
there is not internal cd drive and the external drive that i am using is 
mounted somewhere else. does anyone know a solution to this problem so i 
can get my wifi working? thanks in advance