You'd want to get an antivirus, you can find links to free ones in the sticky.
For cablenut, get the program here: www.cablenut.com
Then open the zip file you specified, or version 8, and extract the .ccs file that is closest to your connection speeds to the desktop. With the cablenut adjuster window open, open the .ccs file, click save to registry, reboot PC and retest.