This should set it to the lowest possible.
Screen resolution might be a different story, but that can be changed.
Code
shadowlevel 0
blood false
bloom false
waterlevel 0
specular false
trace 0
lod 0
backsound2 100.00
effectsound 100.00
gamma 1.00
clipfar 75.00
mapalpha 255
genchatalpha 80
syschatalpha 80
genchatsize 8
syschatsize 6
alwaysontop false
last_server 0
last_channel 0
charnameshow 0
controltype 1
display 1024 768 16
mode false
quality 0
selection 0
condition 0
expression 0
tri_filter false
high_shadow false
trade_mode false
party_mode false
partyPVP_mode false
alliance_mode false
selftarget false
inflow false
outflow false
guild_mode false
friend_mode false
servername_mode false
reception_mode false
mp3_show false
mp3_volume 100.00
mp3_loop 0
pvprequest true
autoUsePotion true
useHpPotionRatio 50.00
useMpPotionRatio 50.00
covermap true
bumpmap true
damage_option 0
chatnormal true true true true true true true
chatparty false true false false true false false
chatguild false false true false true false false
chatguildleader false false false false true true false
chatalliance false false false false true false true