Your download speed depends on your speed, host(s) speed, how many hosts you're downloading from etc. You can only download as fast as the sources' connections allow.

Check out the first few posts of the sticky below - there are good tips for setting up LW.
Configuring LW for best performance

Rather than turning off Norton (I guess it's NPF you're talking about?), configure it to allow LW access
http://www.gnutellaforums.com/showpo...10&postcount=6