Right here's my problem...
I'm trying to configure dhcpd to lease a particular ip to certain hosts on the subnet. However the hosts stick with their existing ips rather than switch to the newly assigned ones...
I've read a guide to dhcp and think i understand it.

below is my config i expected melee to be given 192.168.0.2.. however it sticks with 192.168.0.10

Any Ideas??

# dhcpd.conf
#
# Configuration file for ISC dhcpd (see 'man dhcpd.conf')
#
ddns-update-style none;
option domain-name "Blackmesa";
option domain-name-servers 213.120.62.100, 213.120.62.101;
option routers 192.168.0.1;
max-lease-time 604800;
default-lease-time 604800;
#authoritative;


subnet 192.168.0.0 netmask 255.255.255.0 {
range 192.168.0.2 192.168.0.15;
}

host melee{
fixed-address 192.168.0.2;
}

host 557VP18{
fixed-address 192.168.0.3;
}

The only thing you're missing is a MAC address, and that should be working.

host melee
{
hardware ethernet 00E:AD:BE:EF:00;
fixed-address 192.168.0.2;
}

bentz is right on, but if for some dumb reason that didn't work, you might want to give this a try.
There is a file /var/state/dhcp/dhcpd.lesases
This file contains all of the leases the dhcp server has given out and to which machine. That way if any given machine happens to connect again, it will most likely get the ip address it received before. Delete the entry
lease 192.168.0.10 {
...
...
}