Just set ip's betwenn your p2p with your brother or just use the network connection wizard (those microsoft bast***s must pay) or just set the ip propities on both coms to auto , ethier that or one of you have a bust lan card , crappy lan card , or just a dodge mainboard with dodgie onbard lan , or there is ethier a kink in the cable (meaning the cable would be rooted , unless you play around with it in the place that it's kinked)
have u tried reinstalling hl or esf , are your esf versions the same ? , also make sure the ip's are set right otherwise , you can crash each other's games at start up (example: if u had a ip address set as 192.168.0.10 and the other 192.168.1.1 , the 7th didgit is what needs to be changed)
as far as i know , evm sp is not out , and if u installed the cp , it will make no difference to when you play lan ,