Paste this in your host file and it's fool proof, unless they know the ip addys for the sites them self:
# block myspace.com host names
127.0.0.1 log.myspace.com
127.0.0.1 browseusers.myspace.com
127.0.0.1 classifieds.myspace.com
127.0.0.1 collect.myspace.com
127.0.0.1 events.myspace.com
127.0.0.1 favorites.myspace.com
127.0.0.1 forum.myspace.com
127.0.0.1 groups.myspace.com
127.0.0.1 home.myspace.com
127.0.0.1 invite.myspace.com
127.0.0.1 linux.myspace.com
127.0.0.1 login.myspace.com
127.0.0.1 message.myspace.com
127.0.0.1 messages.myspace.com
127.0.0.1 music.myspace.com
127.0.0.1 mx2.myspace.com
127.0.0.1 myspace.com
127.0.0.1 ns1.myspace.com
127.0.0.1 ns2.myspace.com
127.0.0.1 profile.myspace.com
127.0.0.1 rio.myspace.com
127.0.0.1 search.myspace.com
127.0.0.1 vids.myspace.com
127.0.0.1 viewmorepics.myspace.com
127.0.0.1 vmta01.myspace.com
127.0.0.1 vmta02.myspace.com
127.0.0.1 vmta03.myspace.com
127.0.0.1 vmta04.myspace.com
127.0.0.1 vmta05.myspace.com
127.0.0.1 vmta06.myspace.com
127.0.0.1 vmta07.myspace.com
127.0.0.1 vmta08.myspace.com
127.0.0.1 vmta09.myspace.com
127.0.0.1 vmta10.myspace.com
127.0.0.1 vmta11.myspace.com
127.0.0.1 vmta12.myspace.com
127.0.0.1 vmta13.myspace.com
127.0.0.1
www.myspace.com
127.0.0.1 www1.myspace.com
127.0.0.1 videos.myspace.com
127.0.0.1 mail.myspace.com
127.0.0.1 signup.myspace.com
127.0.0.1 security.myspace.com