Ok, I did a quick search on google and found a HOST file with over 13,000 entries...... It is below.....

In Windows 95-ME the hostfile is in C:\Windows
In Nt/2000/XP it is in C:\WinNT\system32\drivers\etc

Rename this file to HOST (no extension) and replace the old file with this one

If you dont want to see a error page when an ad is blocked try this program

EDIT: The host file comes in two formats, 127.0.0.1 adserver.com and 0.0.0.0 adserver.com, I only included the 0.0.0.0 one because it works better and causes pages to load a lot quicker that the localhost one.... If you want to replace 0.0.0.0 with another IP for a page to show instead of an ad, you may do so, but it does cause considerable network traffic