Rename this file to "hosts" (You may have to go to tools\folder options\view -> uncheck "Hide extensions for known file types" in order to see that it is named hosts.txt) and stick it in C:\WINNT\system32\drivers\etc (where WINNT is either WINNT or Windows, depending on what version of Windblows you have installed)
I forgot where the location to stick it is for Windblows 9x though.